Commit Graph

1408 Commits

Author SHA1 Message Date
Paul E. McKenney ff3bf92d90 torture: Allow inter-stutter interval to be specified
Currently, the inter-stutter interval is the same as the stutter duration,
that is, whatever number of jiffies is passed into torture_stutter_init().
This has worked well for quite some time, but the addition of
forward-progress testing to rcutorture can delay processes for several
seconds, which can triple the time that they are stuttered.

This commit therefore adds a second argument to torture_stutter_init()
that specifies the inter-stutter interval.  While locktorture preserves
the current behavior, rcutorture uses the RCU CPU stall warning interval
to provide a wider inter-stutter interval.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-05-28 09:06:09 -07:00
Paul E. McKenney e8516c64fe rcutorture: Fix stutter_wait() return value and freelist checks
The stutter_wait() function is supposed to return true if it actually
waits and false otherwise, but it instead unconditionally returns false.
Which hides a bug in rcu_torture_writer() that fails to account for
the fact that one of the rcu_tortures[] array elements will normally be
referenced by rcu_torture_current, and thus not be on the freelist.

This commit therefore corrects the stutter_wait() return value and adds a
check for rcu_torture_current to rcu_torture_writer()'s check that things
get freed after everything goes quiescent.  In addition, this commit
causes torture_stutter() to give a bit more than one second (instead of
only one jiffy) warning of the end of the stutter interval.  Finally,
this commit disables long-delay readers and aggressive update-side
forward-progress checks while forward-progress testing is in flight.

Reported-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-05-28 09:06:09 -07:00
Paul E. McKenney 140e53f20b rcutorture: Add cond_resched() to forward-progress free-up loop
The rcu_torture_fwd_prog_cbfree() function frees callbacks used during
rcutorture's call_rcu() forward-progress test, but does so in a tight
loop.  This could cause problems given a very long list of callbacks to be
freed, and actual testing produces lists with as many as 25M callbacks.
This commit therefore adds a cond_resched() to this loop.  While in
the area, this commit also rearranges the lock releases to look a bit
more sane.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-05-28 09:06:09 -07:00
Oleg Nesterov 89da3b94bb rcu/sync: Simplify the state machine
With this patch rcu_sync has a single state variable and the transition rules
become really simple:

	GP_IDLE   - owned by the first rcu_sync_enter() which moves it to

	GP_ENTER  - owned by rcu-callback which moves it to

	GP_PASSED - owned by the last rcu_sync_exit() which moves it to

	GP_EXIT   - and this is the only "nontrivial" state.

		rcu-callback moves it back to GP_IDLE unless another enter()
		comes before a GP pass.

		If rcu-callback is invoked before the next rcu_sync_exit() it
		must see gp_count incremented by that enter() and set GP_PASSED.

		Otherwise, if the next rcu_sync_exit() wins the race, it will
		move it to

	GP_REPLAY - owned by rcu-callback which moves it to GP_EXIT

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
[ paulmck: While here, apply READ_ONCE() and WRITE_ONCE() to ->gp_state. ]
[ paulmck: Tweaks to make htmldocs happy. (Reported by kbuild test robot.) ]
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-05-28 09:05:23 -07:00
Oleg Nesterov 95bf33b55f rcu/sync: Kill rcu_sync_type/gp_type
Now that the RCU flavors have been consolidated, rcu_sync_type makes no
sense because none of internal update functions aside from .held() depend
on gp_type.  This commit therefore removes this field and consolidates
the relevant code.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
[ paulmck: Added RCU and RCU-bh checks to rcu_sync_is_idle(). ]
[ paulmck: And applied subsequent feedback from Oleg Nesterov. ]
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-05-28 09:05:23 -07:00
Jiang Biao 11b000457f rcu: Make __call_srcu static
Because __call_srcu() is not used outside kernel/rcu/srcutree.c,
this commit makes it static.

Signed-off-by: Jiang Biao <benbjiang@tencent.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-05-28 09:03:35 -07:00
Paul E. McKenney fe15b50cde srcu: Allocate per-CPU data for DEFINE_SRCU() in modules
Adding DEFINE_SRCU() or DEFINE_STATIC_SRCU() to a loadable module requires
that the size of the reserved region be increased, which is not something
we want to be doing all that often.  One approach would be to require
that loadable modules define an srcu_struct and invoke init_srcu_struct()
from their module_init function and cleanup_srcu_struct() from their
module_exit function.  However, this is more than a bit user unfriendly.

This commit therefore creates an ___srcu_struct_ptrs linker section,
and pointers to srcu_struct structures created by DEFINE_SRCU() and
DEFINE_STATIC_SRCU() within a module are placed into that module's
___srcu_struct_ptrs section.  The required init_srcu_struct() and
cleanup_srcu_struct() functions are then automatically invoked as needed
when that module is loaded and unloaded, thus allowing modules to continue
to use DEFINE_SRCU() and DEFINE_STATIC_SRCU() while avoiding the need
to increase the size of the reserved region.

Many of the algorithms and some of the code was cheerfully cherry-picked
from other code making use of linker sections, perhaps most notably from
tracepoints.  All bugs are nevertheless the sole property of the author.

Suggested-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
[ paulmck: Use __section() and use "default" in srcu_module_notify()'s
  "switch" statement as suggested by Joel Fernandes. ]
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Tested-by: Joel Fernandes (Google) <joel@joelfernandes.org>
2019-05-28 09:03:35 -07:00
Paul E. McKenney d5a9a8c3bc rcu: Set a maximum limit for back-to-back callback invocation
Currently, if a CPU has more than 10,000 callbacks pending, it will
increase rdp->blimit to LONG_MAX.  If you are lucky, LONG_MAX is only
about two billion, but this is still a bit too many callbacks to invoke
back-to-back while otherwise ignoring the world.

This commit therefore sets a maximum limit of DEFAULT_MAX_RCU_BLIMIT,
which is set to 10,000, for rdp->blimit.

Reported-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-05-28 09:02:57 -07:00
Neeraj Upadhyay 3ae976a7e3 rcu: Correctly unlock root node in rcu_check_gp_start_stall()
On systems whose rcu_node tree has only one node, the
rcu_check_gp_start_stall() function's values of rnp and rnp_root will
be identical.  In this case, it clearly does not make sense to release
both rnp->lock and rnp_root->lock, but that is exactly what this function
does in the last early exit.  This commit therefore unlocks only rnp->lock
when rnp and rnp_root are equal.

Signed-off-by: Neeraj Upadhyay <neeraju@codeaurora.org>
Reviewed-by: Mukesh Ojha <mojha@codeaurora.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-05-28 09:02:57 -07:00
Neeraj Upadhyay cd6d17b4a4 rcu: Dump specified number of blocked tasks
The dump_blkd_tasks() function dumps at most 10 blocked tasks, ignoring
the value of the ncheck parameter.  This commit therefore substitutes
the value of ncheck for the hard-coded value of 10.  Because all callers
currently pass 10 as the number, this patch does not change behavior,
but it is clearly an accident waiting to happen.

Signed-off-by: Neeraj Upadhyay <neeraju@codeaurora.org>
Reviewed-by: Mukesh Ojha <mojha@codeaurora.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-05-28 09:02:57 -07:00
Jiang Biao f0b6356273 rcu: Remove unused rdp local from synchronize_rcu_expedited()
Because rdp is initialized but never used in synchronize_rcu_expedited(),
this commit removes it.

Signed-off-by: Jiang Biao <benbjiang@tencent.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-05-28 08:48:19 -07:00
Paul E. McKenney 1bb336443c rcu: Rename rcu_data's ->deferred_qs to ->exp_deferred_qs
The rcu_data structure's ->deferred_qs field is used to indicate that the
current CPU is blocking an expedited grace period (perhaps a future one).
Given that it is used only for expedited grace periods, its current name
is misleading, so this commit renames it to ->exp_deferred_qs.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-05-28 08:48:19 -07:00
Joel Fernandes (Google) eddded8012 rcu: Add checks for dynticks counters in rcu_is_cpu_rrupt_from_idle()
It would be good to combine the dynticks and dynticks_nesting counters
in order to simplify the code.  Unfortunately, there are concerns
about usermode upcalls appearing to RCU as half of an interrupt, as
Byungchul learned [1].  The "half" in "half interrupt" is due to an
unpaired rcu_irq_enter(): Normally, each rcu_irq_enter() has a later
call to rcu_irq_exit().

Out of an abundance of caution, Paul added warnings [2] in the RCU
code which if not fired by 2021 will be interpreted as meaning that
this half-interrupt scenario cannot happen any more, thus permitting
simplification of this code.

In the meantime, this commit makes the following changes:

(1) Combining these two counters requires that rcu_rrupt_from_idle()
    is invoked only from hard-interrupt contexts as discussed here [3].
    This commit therefore adds the required lockdep_assert_in_irq()
    to check this constraint.

(2) Furthermore, rcu_rrupt_from_idle() is not explicit about how it
    is using the counters which can lead to weird future bugs. This
    commit therefore adds comments indicating the meaning and use of
    each counter.

(3) Lastly, this commit checks for counter underflows as another check
    that half interrupts don't occur.  (Previously, the function would
    simply return true upon underflow.)

All these checks checks are NOOPs if PROVE_LOCKING (and thus PROVE_RCU)
are disabled.

[1] https://lore.kernel.org/patchwork/patch/952349/
[2] Commit e11ec65cc8 ("rcu: Add warning to detect half-interrupts")
[3] https://lore.kernel.org/lkml/20190312150514.GB249405@google.com/

Cc: byungchul.park@lge.com
Cc: kernel-team@android.com
Cc: rcu@vger.kernel.org
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-05-28 08:48:19 -07:00
Paul E. McKenney e015a34112 rcu: Avoid self-IPI in sync_sched_exp_online_cleanup()
The sync_sched_exp_online_cleanup() is invoked at online time to handle
the case where the start of an expedited grace period ran concurrently
with a CPU being taken offline and then immediately being placed online.
It checks to see if RCU needs an expedited quiescent state from the
incoming CPU, sending it an IPI if so.  However, it is quite possible
that sync_sched_exp_online_cleanup() is running on that CPU, in which
case it is considerably less overhead to simply request the quiescent
state locally instead of simulating a self-IPI.

This commit therefore places the last few lines of rcu_exp_handler()
into a new rcu_exp_need_qs() function, which is invoked both by
rcu_exp_handler() and by sync_sched_exp_online_cleanup() in the self-IPI
case.

This also reduces the rcu_exp_handler() function's state space by
removing the direct call that this smp_call_function_single() uses to
emulate the requested self-IPI.  This in turn will allow tighter error
checking in rcu_is_cpu_rrupt_from_idle().

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
2019-05-25 14:50:50 -07:00
Paul E. McKenney b9ad4d6ed1 rcu: Avoid self-IPI in sync_rcu_exp_select_node_cpus()
Although sync_rcu_exp_select_node_cpus() treats the current CPU as being
in a quiescent state, it might well migrate to some other CPU before
reaching the smp_call_function_single(), which could then result in an
unnecessary simulated self-IPI.  This commit therefore instead simply
refuses to invoke smp_call_function_single() on the current CPU, which
causes the later rcu_report_exp_cpu_mult() to report this CPU's quiescent
state with less overhead.

This also reduces the rcu_exp_handler() function's state space by removing
the direct call that this smp_call_function_single() uses to emulate the
requested self-IPI.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
[ paulmck: Use get_cpu() instead of preempt_disable() per Joel Fernandes. ]
2019-05-25 14:50:50 -07:00
Paul E. McKenney 43e903ad3e rcu: Inline invoke_rcu_callbacks() into its sole remaining caller
This commit saves a few lines of code by inlining invoke_rcu_callbacks()
into its sole remaining caller.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-05-25 14:50:49 -07:00
Paul E. McKenney 0864f057b0 rcu: Use irq_work to get scheduler's attention in clean context
When rcu_read_unlock_special() is invoked with interrupts disabled, is
either not in an interrupt handler or is not using RCU_SOFTIRQ, is not
the first RCU read-side critical section in the chain, and either there
is an expedited grace period in flight or this is a NO_HZ_FULL kernel,
the end of the grace period can be unduly delayed.  The reason for this
is that it is not safe to do wakeups in this situation.

This commit fixes this problem by using the irq_work subsystem to
force a later interrupt handler in a clean environment.  Because
set_tsk_need_resched(current) and set_preempt_need_resched() are
invoked prior to this, the scheduler will force a context switch
upon return from this interrupt (though perhaps at the end of any
interrupted preempt-disable or BH-disable region of code), which will
invoke rcu_note_context_switch() (again in a clean environment), which
will in turn give RCU the chance to report the deferred quiescent state.

Of course, by then this task might be within another RCU read-side
critical section.  But that will be detected at that time and reporting
will be further deferred to the outermost rcu_read_unlock().  See
rcu_preempt_need_deferred_qs() and rcu_preempt_deferred_qs() for more
details on the checking.

Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-05-25 14:50:49 -07:00
Paul E. McKenney 385b599e8c rcu: Allow rcu_read_unlock_special() to raise_softirq() if in_irq()
When running in an interrupt handler, raise_softirq() and
raise_softirq_irqoff() have extremely low overhead: They simply set a
bit in a per-CPU mask, which is checked upon exit from that interrupt
handler.  Therefore, if rcu_read_unlock_special() is invoked within an
interrupt handler and RCU_SOFTIRQ is in use, this commit make use of
raise_softirq_irqoff() even if there is no expedited grace period in
flight and even if this is not a nohz_full CPU.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-05-25 14:50:48 -07:00
Paul E. McKenney 25102de65f rcu: Only do rcu_read_unlock_special() wakeups if expedited
Currently, rcu_read_unlock_special() will do wakeups whenever it is safe
to do so.  However, wakeups are expensive, and they are only really
needed when the just-ended RCU read-side critical section is blocking
an expedited grace period (in which case speed is of the essence)
or on a nohz_full CPU (where it might be a good long time before an
interrupt arrives).  This commit therefore checks for these conditions,
and does the expensive wakeups only if doing so would be useful.

Note it can be rather expensive to determine whether or not the current
task (as opposed to the current CPU) is blocking the current expedited
grace period.  Doing so requires traversing the ->blkd_tasks list, which
can be quite long.  This commit therefore cheats:  If the current task
is on a given ->blkd_tasks list, and some task on that list is blocking
the current expedited grace period, the code assumes that the current
task is blocking that expedited grace period.

Reported-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-05-25 14:50:48 -07:00
Paul E. McKenney 23634ebc1d rcu: Check for wakeup-safe conditions in rcu_read_unlock_special()
When RCU core processing is offloaded from RCU_SOFTIRQ to the rcuc
kthreads, a full and unconditional wakeup is required to initiate RCU
core processing.  In contrast, when RCU core processing is carried
out by RCU_SOFTIRQ, a raise_softirq() suffices.  Of course, there are
situations where raise_softirq() does a full wakeup, but these do not
occur with normal usage of rcu_read_unlock().

The reason that full wakeups can be problematic is that the scheduler
sometimes invokes rcu_read_unlock() with its pi or rq locks held,
which can of course result in deadlock in CONFIG_PREEMPT=y kernels when
rcu_read_unlock() invokes the scheduler.  Scheduler invocations can happen
in the following situations: (1) The just-ended reader has been subjected
to RCU priority boosting, in which case rcu_read_unlock() must deboost,
(2) Interrupts were disabled across the call to rcu_read_unlock(), so
the quiescent state must be deferred, requiring a wakeup of the rcuc
kthread corresponding to the current CPU.

Now, the scheduler may hold one of its locks across rcu_read_unlock()
only if preemption has been disabled across the entire RCU read-side
critical section, which in the days prior to RCU flavor consolidation
meant that rcu_read_unlock() never needed to do wakeups.  However, this
is no longer the case for any but the first rcu_read_unlock() following a
condition (e.g., preempted RCU reader) requiring special rcu_read_unlock()
attention.  For example, an RCU read-side critical section might be
preempted, but preemption might be disabled across the rcu_read_unlock().
The rcu_read_unlock() must defer the quiescent state, and therefore
leaves the task queued on its leaf rcu_node structure.  If a scheduler
interrupt occurs, the scheduler might well invoke rcu_read_unlock() with
one of its locks held.  However, the preempted task is still queued, so
rcu_read_unlock() will attempt to defer the quiescent state once more.
When RCU core processing is carried out by RCU_SOFTIRQ, this works just
fine: The raise_softirq() function simply sets a bit in a per-CPU mask
and the RCU core processing will be undertaken upon return from interrupt.

Not so when RCU core processing is carried out by the rcuc kthread: In this
case, the required wakeup can result in deadlock.

The initial solution to this problem was to use set_tsk_need_resched() and
set_preempt_need_resched() to force a future context switch, which allows
rcu_preempt_note_context_switch() to report the deferred quiescent state
to RCU's core processing.  Unfortunately for expedited grace periods,
there can be a significant delay between the call for a context switch
and the actual context switch.

This commit therefore introduces a ->deferred_qs flag to the task_struct
structure's rcu_special structure.  This flag is initially false, and
is set to true by the first call to rcu_read_unlock() requiring special
attention, then finally reset back to false when the quiescent state is
finally reported.  Then rcu_read_unlock() attempts full wakeups only when
->deferred_qs is false, that is, on the first rcu_read_unlock() requiring
special attention.  Note that a chain of RCU readers linked by some other
sort of reader may find that a later rcu_read_unlock() is once again able
to do a full wakeup, courtesy of an intervening preemption:

	rcu_read_lock();
	/* preempted */
	local_irq_disable();
	rcu_read_unlock(); /* Can do full wakeup, sets ->deferred_qs. */
	rcu_read_lock();
	local_irq_enable();
	preempt_disable()
	rcu_read_unlock(); /* Cannot do full wakeup, ->deferred_qs set. */
	rcu_read_lock();
	preempt_enable();
	/* preempted, >deferred_qs reset. */
	local_irq_disable();
	rcu_read_unlock(); /* Can again do full wakeup, sets ->deferred_qs. */

Such linked RCU readers do not yet seem to appear in the Linux kernel, and
it is probably best if they don't.  However, RCU needs to handle them, and
some variations on this theme could make even raise_softirq() unsafe due to
the possibility of its doing a full wakeup.  This commit therefore also
avoids invoking raise_softirq() when the ->deferred_qs set flag is set.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
2019-05-25 14:50:47 -07:00
Sebastian Andrzej Siewior 48d07c04b4 rcu: Enable elimination of Tree-RCU softirq processing
Some workloads need to change kthread priority for RCU core processing
without affecting other softirq work.  This commit therefore introduces
the rcutree.use_softirq kernel boot parameter, which moves the RCU core
work from softirq to a per-CPU SCHED_OTHER kthread named rcuc.  Use of
SCHED_OTHER approach avoids the scalability problems that appeared
with the earlier attempt to move RCU core processing to from softirq
to kthreads.  That said, kernels built with RCU_BOOST=y will run the
rcuc kthreads at the RCU-boosting priority.

Note that rcutree.use_softirq=0 must be specified to move RCU core
processing to the rcuc kthreads: rcutree.use_softirq=1 is the default.

Reported-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
[ paulmck: Adjust for invoke_rcu_callbacks() only ever being invoked
  from RCU core processing, in contrast to softirq->rcuc transition
  in old mainline RCU priority boosting. ]
[ paulmck: Avoid wakeups when scheduler might have invoked rcu_read_unlock()
  while holding rq or pi locks, also possibly fixing a pre-existing latent
  bug involving raise_softirq()-induced wakeups. ]
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-05-25 14:50:46 -07:00
Thomas Gleixner ec8f24b7fa treewide: Add SPDX license identifier - Makefile/Kconfig
Add SPDX license identifiers to all Make/Kconfig files which:

 - Have no license information of any form

These files fall under the project license, GPL v2 only. The resulting SPDX
license identifier is:

  GPL-2.0-only

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2019-05-21 10:50:46 +02:00
Linus Torvalds d2d8b14604 The major changes in this tracing update includes:
- Removing of non-DYNAMIC_FTRACE from 32bit x86
 
  - Removing of mcount support from x86
 
  - Emulating a call from int3 on x86_64, fixes live kernel patching
 
  - Consolidated Tracing Error logs file
 
 Minor updates:
 
  - Removal of klp_check_compiler_support()
 
  - kdb ftrace dumping output changes
 
  - Accessing and creating ftrace instances from inside the kernel
 
  - Clean up of #define if macro
 
  - Introduction of TRACE_EVENT_NOP() to disable trace events based on config
    options
 
 And other minor fixes and clean ups
 -----BEGIN PGP SIGNATURE-----
 
 iIoEABYIADIWIQRRSw7ePDh/lE+zeZMp5XQQmuv6qgUCXNxMZxQccm9zdGVkdEBn
 b29kbWlzLm9yZwAKCRAp5XQQmuv6qq4PAP44kP6VbwL8CHyI2A3xuJ6Hwxd+2Z2r
 ip66RtzyJ+2iCgEA2QCuWUlEt2bLpF9a8IQ4N9tWenSeW2i7gunPb+tioQw=
 =RVQo
 -----END PGP SIGNATURE-----

Merge tag 'trace-v5.2' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace

Pull tracing updates from Steven Rostedt:
 "The major changes in this tracing update includes:

   - Removal of non-DYNAMIC_FTRACE from 32bit x86

   - Removal of mcount support from x86

   - Emulating a call from int3 on x86_64, fixes live kernel patching

   - Consolidated Tracing Error logs file

  Minor updates:

   - Removal of klp_check_compiler_support()

   - kdb ftrace dumping output changes

   - Accessing and creating ftrace instances from inside the kernel

   - Clean up of #define if macro

   - Introduction of TRACE_EVENT_NOP() to disable trace events based on
     config options

  And other minor fixes and clean ups"

* tag 'trace-v5.2' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace: (44 commits)
  x86: Hide the int3_emulate_call/jmp functions from UML
  livepatch: Remove klp_check_compiler_support()
  ftrace/x86: Remove mcount support
  ftrace/x86_32: Remove support for non DYNAMIC_FTRACE
  tracing: Simplify "if" macro code
  tracing: Fix documentation about disabling options using trace_options
  tracing: Replace kzalloc with kcalloc
  tracing: Fix partial reading of trace event's id file
  tracing: Allow RCU to run between postponed startup tests
  tracing: Fix white space issues in parse_pred() function
  tracing: Eliminate const char[] auto variables
  ring-buffer: Fix mispelling of Calculate
  tracing: probeevent: Fix to make the type of $comm string
  tracing: probeevent: Do not accumulate on ret variable
  tracing: uprobes: Re-enable $comm support for uprobe events
  ftrace/x86_64: Emulate call function while updating in breakpoint handler
  x86_64: Allow breakpoints to emulate call instructions
  x86_64: Add gap to int3 to allow for call emulation
  tracing: kdb: Allow ftdump to skip all but the last few entries
  tracing: Add trace_total_entries() / trace_total_entries_cpu()
  ...
2019-05-15 16:05:47 -07:00
Linus Torvalds 0968621917 Printk changes for 5.2
-----BEGIN PGP SIGNATURE-----
 
 iQIzBAABCAAdFiEESH4wyp42V4tXvYsjUqAMR0iAlPIFAlzP8nQACgkQUqAMR0iA
 lPK79A/+NkRouqA9ihAZhUbgW0DHzOAFvUJSBgX11HQAZbGjngakuoyYFvwUx0T0
 m80SUTCysxQrWl+xLdccPZ9ZrhP2KFQrEBEdeYHZ6ymcYcl83+3bOIBS7VwdZAbO
 EzB8u/58uU/sI6ABL4lF7ZF/+R+U4CXveEUoVUF04bxdPOxZkRX4PT8u3DzCc+RK
 r4yhwQUXGcKrHa2GrRL3GXKsDxcnRdFef/nzq4RFSZsi0bpskzEj34WrvctV6j+k
 FH/R3kEcZrtKIMPOCoDMMWq07yNqK/QKj0MJlGoAlwfK4INgcrSXLOx+pAmr6BNq
 uMKpkxCFhnkZVKgA/GbKEGzFf+ZGz9+2trSFka9LD2Ig6DIstwXqpAgiUK8JFQYj
 lq1mTaJZD3DfF2vnGHGeAfBFG3XETv+mIT/ow6BcZi3NyNSVIaqa5GAR+lMc6xkR
 waNkcMDkzLFuP1r0p7ZizXOksk9dFkMP3M6KqJomRtApwbSNmtt+O2jvyLPvB3+w
 wRyN9WT7IJZYo4v0rrD5Bl6BjV15ZeCPRSFZRYofX+vhcqJQsFX1M9DeoNqokh55
 Cri8f6MxGzBVjE1G70y2/cAFFvKEKJud0NUIMEuIbcy+xNrEAWPF8JhiwpKKnU10
 c0u674iqHJ2HeVsYWZF0zqzqQ6E1Idhg/PrXfuVuhAaL5jIOnYY=
 =WZfC
 -----END PGP SIGNATURE-----

Merge tag 'printk-for-5.2' of git://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk

Pull printk updates from Petr Mladek:

 - Allow state reset of printk_once() calls.

 - Prevent crashes when dereferencing invalid pointers in vsprintf().
   Only the first byte is checked for simplicity.

 - Make vsprintf warnings consistent and inlined.

 - Treewide conversion of obsolete %pf, %pF to %ps, %pF printf
   modifiers.

 - Some clean up of vsprintf and test_printf code.

* tag 'printk-for-5.2' of git://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk:
  lib/vsprintf: Make function pointer_string static
  vsprintf: Limit the length of inlined error messages
  vsprintf: Avoid confusion between invalid address and value
  vsprintf: Prevent crash when dereferencing invalid pointers
  vsprintf: Consolidate handling of unknown pointer specifiers
  vsprintf: Factor out %pO handler as kobject_string()
  vsprintf: Factor out %pV handler as va_format()
  vsprintf: Factor out %p[iI] handler as ip_addr_string()
  vsprintf: Do not check address of well-known strings
  vsprintf: Consistent %pK handling for kptr_restrict == 0
  vsprintf: Shuffle restricted_pointer()
  printk: Tie printk_once / printk_deferred_once into .data.once for reset
  treewide: Switch printk users from %pf and %pF to %ps and %pS, respectively
  lib/test_printf: Switch to bitmap_zalloc()
2019-05-07 09:18:12 -07:00
Paul E. McKenney 6cdbc07a5a Merge branches 'consolidate.2019.04.09a', 'doc.2019.03.26b', 'fixes.2019.03.26b', 'srcu.2019.03.26b', 'stall.2019.03.26b' and 'torture.2019.03.26b' into HEAD
consolidate.2019.04.09a: Lingering RCU flavor consolidation cleanups.
doc.2019.03.26b: Documentation updates.
fixes.2019.03.26b: Miscellaneous fixes.
srcu.2019.03.26b: SRCU updates.
stall.2019.03.26b: RCU CPU stall warning updates.
torture.2019.03.26b: Torture-test updates.
2019-04-09 08:08:13 -07:00
Sakari Ailus d75f773c86 treewide: Switch printk users from %pf and %pF to %ps and %pS, respectively
%pF and %pf are functionally equivalent to %pS and %ps conversion
specifiers. The former are deprecated, therefore switch the current users
to use the preferred variant.

The changes have been produced by the following command:

	git grep -l '%p[fF]' | grep -v '^\(tools\|Documentation\)/' | \
	while read i; do perl -i -pe 's/%pf/%ps/g; s/%pF/%pS/g;' $i; done

And verifying the result.

Link: http://lkml.kernel.org/r/20190325193229.23390-1-sakari.ailus@linux.intel.com
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: sparclinux@vger.kernel.org
Cc: linux-um@lists.infradead.org
Cc: xen-devel@lists.xenproject.org
Cc: linux-acpi@vger.kernel.org
Cc: linux-pm@vger.kernel.org
Cc: drbd-dev@lists.linbit.com
Cc: linux-block@vger.kernel.org
Cc: linux-mmc@vger.kernel.org
Cc: linux-nvdimm@lists.01.org
Cc: linux-pci@vger.kernel.org
Cc: linux-scsi@vger.kernel.org
Cc: linux-btrfs@vger.kernel.org
Cc: linux-f2fs-devel@lists.sourceforge.net
Cc: linux-mm@kvack.org
Cc: ceph-devel@vger.kernel.org
Cc: netdev@vger.kernel.org
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Acked-by: David Sterba <dsterba@suse.com> (for btrfs)
Acked-by: Mike Rapoport <rppt@linux.ibm.com> (for mm/memblock.c)
Acked-by: Bjorn Helgaas <bhelgaas@google.com> (for drivers/pci)
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
2019-04-09 14:19:06 +02:00
Yafang Shao 4f5fbd78a7 rcu: validate arguments for rcu tracepoints
When CONFIG_RCU_TRACE is not set, all these tracepoints are defined as
do-nothing macro.
We'd better make those inline functions that take proper arguments.

As RCU_TRACE() is defined as do-nothing marco as well when
CONFIG_RCU_TRACE is not set, so we can clean it up.

Link: http://lkml.kernel.org/r/1553602391-11926-4-git-send-email-laoar.shao@gmail.com

Reviewed-by: Paul E. McKenney <paulmck@linux.ibm.com>
Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
2019-04-08 09:22:51 -04:00
Paul E. McKenney ad092c0277 rcuperf: Fix cleanup path for invalid perf_type strings
If the specified rcuperf.perf_type is not in the rcu_perf_init()
function's perf_ops[] array, rcuperf prints some console messages and
then invokes rcu_perf_cleanup() to set state so that a future torture
test can run.  However, rcu_perf_cleanup() also attempts to end the
test that didn't actually start, and in doing so relies on the value
of cur_ops, a value that is not particularly relevant in this case.
This can result in confusing output or even follow-on failures due to
attempts to use facilities that have not been properly initialized.

This commit therefore sets the value of cur_ops to NULL in this case and
inserts a check near the beginning of rcu_perf_cleanup(), thus avoiding
relying on an irrelevant cur_ops value.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-03-26 14:42:53 -07:00
Paul E. McKenney b813afae7a rcutorture: Fix cleanup path for invalid torture_type strings
If the specified rcutorture.torture_type is not in the rcu_torture_init()
function's torture_ops[] array, rcutorture prints some console messages
and then invokes rcu_torture_cleanup() to set state so that a future
torture test can run.  However, rcu_torture_cleanup() also attempts to
end the test that didn't actually start, and in doing so relies on the
value of cur_ops, a value that is not particularly relevant in this case.
This can result in confusing output or even follow-on failures due to
attempts to use facilities that have not been properly initialized.

This commit therefore sets the value of cur_ops to NULL in this case
and inserts a check near the beginning of rcu_torture_cleanup(),
thus avoiding relying on an irrelevant cur_ops value.

Reported-by: kernel test robot <rong.a.chen@intel.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-03-26 14:42:53 -07:00
Neeraj Upadhyay d44ac1bebc rcutorture: Fix expected forward progress duration in OOM notifier
The rcutorture_oom_notify() function has a misplaced close parenthesis
that results in increasingly long delays in rcu_fwd_progress_check()'s
checking for various RCU forward-progress problems.  This commit therefore
puts the parenthesis in the right place.

Signed-off-by: Neeraj Upadhyay <neeraju@codeaurora.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-03-26 14:42:53 -07:00
Paul E. McKenney f47cb1bb0d rcutorture: Remove ->ext_irq_conflict field
Back when there was a separate RCU-bh flavor, the ->ext_irq_conflict
field was used to prevent executing local_bh_enable() while interrupts
were disabled.  However, there is no longer an RCU-bh flavor, so this
commit removes the no-longer-needed ->ext_irq_conflict field.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-03-26 14:42:53 -07:00
Paul E. McKenney a3b0e1e59e rcutorture: Make rcutorture_extend_mask() comment match the code
The code actually rarely uses more than one type of RCU read-side
protection, as is actually desired given that we need some reasonable
probability of preempting RCU read-side critical sections, which cannot
happen with multiple types of protection.  This comment therefore adjusts
the comment.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-03-26 14:42:53 -07:00
Neeraj Upadhyay 6c70e9cd5f rcu: Fix nohz status in stall warning
The Documentation/RCU/stallwarn.txt file says that stall warnings
print "D" if dyntick-idle processing is enabled, but the code in
print_cpu_stall_fast_no_hz() prints "." instead.  This commit therefore
reverses the sense of the test to make the code match the documentation.

Signed-off-by: Neeraj Upadhyay <neeraju@codeaurora.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-03-26 14:42:00 -07:00
Paul E. McKenney b51bcbbf16 rcu: Move forward-progress checkers into tree_stall.h
This commit further consolidates stall-warning functionality by moving
forward-progress checkers into kernel/rcu/tree_stall.h, updating a
comment or two while in the area.  More specifically, this commit moves
show_rcu_gp_kthreads(), rcu_check_gp_start_stall(), rcu_fwd_progress_check(),
sysrq_rcu, sysrq_show_rcu(), sysrq_rcudump_op, and rcu_sysrq_init() from
kernel/rcu/tree.c to kernel/rcu/tree_stall.h.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-03-26 14:40:13 -07:00
Paul E. McKenney 7ac1907c9e rcu: Move irq-disabled stall-warning checking to tree_stall.h
The rcu_iw_handler() function's sole purpose in life is to indicate
whether a stalled CPU had interrupts disabled, so it belongs in
kernel/rcu/tree_stall.h.  This commit therefore makes that move,
clarifying its header comment while in the area.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-03-26 14:40:13 -07:00
Paul E. McKenney e23344c2ca rcu: Organize functions in tree_stall.h
This commit does only code movement, removal of now-unneeded forward
declarations, and addition of comments.  It organizes the functions
that implement RCU CPU stall warnings for normal grace periods into
three categories:

1.	Control of RCU CPU stall warnings, including computing timeouts.

2.	Interaction of stall warnings with grace periods.

3.	Actual printing of the RCU CPU stall-warning messages.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-03-26 14:40:13 -07:00
Paul E. McKenney 59b73a2768 rcu: Move FAST_NO_HZ stall-warning code to tree_stall.h
This commit further consolidates the stall-warning code by moving
print_cpu_stall_info() and its helper functions along with
zero_cpu_stall_ticks() to kernel/rcu/tree_stall.h.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-03-26 14:40:13 -07:00
Paul E. McKenney 40e69ac7d0 rcu: Inline RCU stall-warning info helper functions
The print_cpu_stall_info_begin() and print_cpu_stall_info_end() print a
single character each onto the console, and are a holdover from a time
when RCU CPU stall warning messages could be abbreviated using a long-gone
Kconfig option.  This commit therefore adds these single characters to
already-printed strings in the calling functions, and then eliminates
both print_cpu_stall_info_begin() and print_cpu_stall_info_end().

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-03-26 14:40:13 -07:00
Paul E. McKenney d87cda5094 rcu: Move rcu_print_task_exp_stall() to tree_exp.h
Because expedited CPU stall warnings are contained within the
kernel/rcu/tree_exp.h file, rcu_print_task_exp_stall() should live
there too.  This commit carries out the required code motion.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-03-26 14:40:13 -07:00
Paul E. McKenney 21d0d79ab0 rcu: Inline RCU task stall-warning helper functions
The rcu_print_detail_task_stall(), rcu_print_task_stall_begin(), and
rcu_print_task_stall_end() functions were defined to allow long-gone
Kconfig options to provide an abbreviated RCU CPU stall warning printout.
This commit saves a few lines of code by inlining them into their sole
callers.

While in the area, a useless call of rcu_print_detail_task_stall_rnp()
on the root rcu_node structure was eliminated.  If there is only one
rcu_node structure, its tasks get printed twice, but if there are more,
the root rcu_node structure is guaranteed to have an empty list of blocked
tasks, hence the uselessness.  (Long ago, root rcu_node structures with
non-empty ->blkd_tasks lists could happen, but no longer.)

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-03-26 14:40:13 -07:00
Paul E. McKenney 32255d51b6 rcu: Move RCU CPU stall-warning code out of tree.c
This commit completes the process of consolidating the code for RCU CPU
stall warnings for normal grace periods by moving the remaining such
code from kernel/rcu/tree.c to kernel/rcu/tree_stall.h.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-03-26 14:40:13 -07:00
Paul E. McKenney 3fc3d1709f rcu: Move RCU CPU stall-warning code out of tree_plugin.h
The RCU CPU stall-warning code for normal grace periods is currently
scattered across two files, due to earlier Tiny RCU support for RCU
CPU stall warnings and for old Kconfig options that have long since
been retired.  Given that it is hard for the lead RCU maintainer to
find relevant stall-warning code, it would be good to consolidate it.
This commit continues this process by moving stall-warning code from
kernel/rcu/tree_plugin.c to a new kernel/rcu/tree_stall.h file.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-03-26 14:40:13 -07:00
Paul E. McKenney 10462d6f58 rcu: Move RCU CPU stall-warning code out of update.c
The RCU CPU stall-warning code for normal grace periods is currently
scattered across three files, due to earlier Tiny RCU support for RCU
CPU stall warnings and for old Kconfig options that have long since
been retired.  Given that it is hard for the lead RCU maintainer to
find relevant stall-warning code, it would be good to consolidate it.
This commit starts this process by moving stall-warning code from
kernel/rcu/update.c to a new kernel/rcu/tree_stall.h file.

Note that the definitions of rcu_cpu_stall_suppress and
rcu_cpu_stall_timeout must remain in kernel/rcu/update.h to provide
compatibility for kernel boot parameter lists.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-03-26 14:40:13 -07:00
Paul E. McKenney f5ad399149 srcu: Remove cleanup_srcu_struct_quiesced()
The cleanup_srcu_struct_quiesced() function was added because NVME
used WQ_MEM_RECLAIM workqueues and SRCU did not, which meant that
NVME workqueues waiting on SRCU workqueues could result in deadlocks
during low-memory conditions.  However, SRCU now also has WQ_MEM_RECLAIM
workqueues, so there is no longer a potential for deadlock.  Furthermore,
it turns out to be extremely hard to use cleanup_srcu_struct_quiesced()
correctly due to the fact that SRCU callback invocation accesses the
srcu_struct structure's per-CPU data area just after callbacks are
invoked.  Therefore, the usual practice of using srcu_barrier() to wait
for callbacks to be invoked before invoking cleanup_srcu_struct_quiesced()
fails because SRCU's callback-invocation workqueue handler might be
delayed, which can result in cleanup_srcu_struct_quiesced() being invoked
(and thus freeing the per-CPU data) before the SRCU's callback-invocation
workqueue handler is finished using that per-CPU data.  Nor is this a
theoretical problem: KASAN emitted use-after-free warnings because of
this problem on actual runs.

In short, NVME can now safely invoke cleanup_srcu_struct(), which
avoids the use-after-free scenario.  And cleanup_srcu_struct_quiesced()
is quite difficult to use safely.  This commit therefore removes
cleanup_srcu_struct_quiesced(), switching its sole user back to
cleanup_srcu_struct().  This effectively reverts the following pair
of commits:

f7194ac32c ("srcu: Add cleanup_srcu_struct_quiesced()")
4317228ad9 ("nvme: Avoid flush dependency in delete controller flow")

Reported-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Tested-by: Bart Van Assche <bvanassche@acm.org>
2019-03-26 14:39:24 -07:00
Paul E. McKenney 5cdfd174ea srcu: Check for in-flight callbacks in _cleanup_srcu_struct()
If someone fails to drain the corresponding SRCU callbacks (for
example, by failing to invoke srcu_barrier()) before invoking either
cleanup_srcu_struct() or cleanup_srcu_struct_quiesced(), the resulting
diagnostic is an ambiguous use-after-free diagnostic, and even then
only if you are running something like KASAN.  This commit therefore
improves SRCU diagnostics by adding checks for in-flight callbacks at
_cleanup_srcu_struct() time.

Note that these diagnostics can still be defeated, for example, by
invoking call_srcu() concurrently with cleanup_srcu_struct().  Which is
a really bad idea, but sometimes all too easy to do.  But even then,
these diagnostics have at least some probability of catching the problem.

Reported-by: Sagi Grimberg <sagi@grimberg.me>
Reported-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Tested-by: Bart Van Assche <bvanassche@acm.org>
2019-03-26 14:39:24 -07:00
Paul E. McKenney add0d37b4f rcu: Correct READ_ONCE()/WRITE_ONCE() for ->rcu_read_unlock_special
The task_struct structure's ->rcu_read_unlock_special field is only ever
read or written by the owning task, but it is accessed both at process
and interrupt levels.  It may therefore be accessed using plain reads
and writes while interrupts are disabled, but must be accessed using
READ_ONCE() and WRITE_ONCE() or better otherwise.  This commit makes a
few adjustments to align with this discipline.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-03-26 14:38:38 -07:00
Paul E. McKenney f1a98045ab rcu: Fix typo in tree_exp.h comment
This commit changes a rcu_exp_handler() comment from rcu_preempt_defer_qs()
to rcu_preempt_deferred_qs() in order to better match reality.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-03-26 14:38:38 -07:00
Paul E. McKenney a2badefa85 rcu: Eliminate redundant NULL-pointer check
Because rcu_wake_cond() checks for a null task_struct pointer, there is
no need for its callers to do so.  This commit eliminates the redundant
check.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-03-26 14:38:38 -07:00
Zhouyi Zhou 5d8a752e31 rcu: Fix force_qs_rnp() header comment
Previously, threads blocked on offlining CPUS were migrated to the
root rcu_node structure, thus requiring RCU priority boosting on this
structure.  However, since commit d19fb8d1f3 ("rcu: Don't migrate
blocked tasks even if all corresponding CPUs offline"), RCU does not
migrate blocked tasks.  Consequently, RCU no longer does RCU priority
boosting on the root rcu_node structure as of commit 1be0085b51 ("rcu:
Don't initiate RCU priority boosting on root rcu_node").

This commit therefore brings comments for the force_qs_rnp() function's
header comment in line with this new no-root-boosting reality.

Signed-off-by: Zhouyi Zhou <zhouzhouyi@gmail.com>
[ paulmck: Also remove obsolete comment on suppressing new grace periods. ]
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-03-26 14:38:38 -07:00
Paul E. McKenney 85f2b60c43 rcu: Update jiffies_to_sched_qs and adjust_jiffies_till_sched_qs() comments
This commit better documents the jiffies_to_sched_qs default-value
strategy used by adjust_jiffies_till_sched_qs()

Reported-by: Joel Fernandes <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-03-26 14:38:38 -07:00
Neeraj Upadhyay 6973032a60 rcu: Default jiffies_to_sched_qs to jiffies_till_sched_qs
The current code only calls adjust_jiffies_till_sched_qs() if
jiffies_till_sched_qs is left at its default value, so when the
jiffies_till_sched_qs kernel-boot parameter actually is specified,
jiffies_to_sched_qs will be left with the value zero, which
will result in useless slowdowns of cond_resched().  This commit
therefore changes rcu_init_geometry() to unconditionally invoke
adjust_jiffies_till_sched_qs(), which ensures that jiffies_to_sched_qs
will be initialized in all cases, thus maintaining good cond_resched()
performance.

Signed-off-by: Neeraj Upadhyay <neeraju@codeaurora.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-03-26 14:38:38 -07:00
Neeraj Upadhyay 0f58d2ac2c rcu: Fix self-wakeups for grace-period kthread
The current rcu_gp_kthread_wake() function uses in_interrupt()
and thus does a self-wakeup from all interrupt contexts, including
the pointless case where the GP kthread happens to be running with
bottom halves disabled, along with the impossible case where the GP
kthread is running within an NMI handler (you are not supposed to invoke
rcu_gp_kthread_wake() from within an NMI handler.  This commit therefore
replaces the in_interrupt() with in_irq(), so that the self-wakeups
happen only from handlers for hardware interrupts and softirqs.
This also makes the code match the comment.

Signed-off-by: Neeraj Upadhyay <neeraju@codeaurora.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
2019-03-26 14:37:49 -07:00
Paul E. McKenney 497e42600b rcu: Report error for bad rcu_nocbs= parameter values
This commit prints a console message when cpulist_parse() reports a
bad list of CPUs, and sets all CPUs' bits in that case.  The reason for
setting all CPUs' bits is that this is the safe(r) choice for real-time
workloads, which would normally be the ones using the rcu_nocbs= kernel
boot parameter.  Either way, later RCU console log messages list the
actual set of CPUs whose RCU callbacks will be offloaded.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-03-26 14:37:49 -07:00
Paul E. McKenney da8739f23f rcu: Allow rcu_nocbs= to specify all CPUs
Currently, the rcu_nocbs= kernel boot parameter requires that a specific
list of CPUs be specified, and has no way to say "all of them".
As noted by user RavFX in a comment to Phoronix topic 1002538, this
is an inconvenient side effect of the removal of the RCU_NOCB_CPU_ALL
Kconfig option.  This commit therefore enables the rcu_nocbs= kernel boot
parameter to be given the string "all", as in "rcu_nocbs=all" to specify
that all CPUs on the system are to have their RCU callbacks offloaded.

Another approach would be to make cpulist_parse() check for "all", but
there are uses of cpulist_parse() that do other checking, which could
conflict with an "all".  This commit therefore focuses on the specific
use of cpulist_parse() in rcu_nocb_setup().

Just a note to other people who would like changes to Linux-kernel RCU:
If you send your requests to me directly, they might get fixed somewhat
faster.  RavFX's comment was posted on January 22, 2018 and I first saw
it on March 5, 2019.  And the only reason that I found it -at- -all- was
that I was looking for projects using RCU, and my search engine showed
me that Phoronix comment quite by accident.  Your choice, though!  ;-)

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-03-26 14:37:49 -07:00
Akira Yokosawa b2eb85b49a rcu: Move common code out of if-else block
As the result of recent addition of "rdp->core_needs_qs = false;" in
the "if" block, now both branches of the if-else have the same
assignment.

Factor it out and reduce line count.

Signed-off-by: Akira Yokosawa <akiyks@gmail.com>
Cc: Joel Fernandes <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Acked-by: Joel Fernandes (Google) <joel@joelfernandes.org>
2019-03-26 14:37:49 -07:00
Liu Song 3ffe3d1adc rcu: Set rcutree.kthread_prio sysfs access to read-only
The rcutree.kthread_prio kernel-boot parameter is used to set the
priority for boost (rcub), per-CPU (rcuc), and grace-period (rcu_preempt
or rcu_sched) kthreads.  It is also used by rcutorture to check whether
it is possible to meaningfully test RCU priority boosting.  However,
all of these cases will either ignore or be confused by any post-boot
changes to rcutree.kthread_prio.

Note that the user really can change the priorities of all of these
kthreads using chrt, given sufficient privileges.  Therefore, the
read-write nature of sysfs access to rcutree.kthread_prio is thus at
best an attractive nuisance.

This commit therefore changes sysfs access to rcutree.kthread_prio to
be read-only.

Signed-off-by: Liu Song <liu.song11@zte.com.cn>
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-03-26 14:37:49 -07:00
Paul E. McKenney 884157cef0 rcu: Make exit_rcu() handle non-preempted RCU readers
The purpose of exit_rcu() is to handle cases where buggy code causes a
task to exit within an RCU read-side critical section.  It currently
does that in the case where said RCU read-side critical section was
preempted at least once, but fails to handle cases where preemption did
not occur.  This case needs to be handled because otherwise the final
context switch away from the exiting task will incorrectly behave as if
task exit were instead a preemption of an RCU read-side critical section,
and will therefore queue the exiting task.  The exiting task will have
exited, and thus won't ever execute rcu_read_unlock(), which means that
it will remain queued forever, blocking all subsequent grace periods,
and eventually resulting in OOM.

Although this is arguably better than letting grace periods proceed
and having a later rcu_read_unlock() access the now-freed task
structure that once belonged to the exiting tasks, it would obviously
be better to correctly handle this case.  This commit therefore sets
->rcu_read_lock_nesting to 1 in that case, so that the subsequence call
to __rcu_read_unlock() causes the exiting task to exit its dangling RCU
read-side critical section.

Note that deferred quiescent states need not be considered.  The reason
is that removing the task from the ->blkd_tasks[] list in the call to
rcu_preempt_deferred_qs() handles the per-task component of any deferred
quiescent state, and all other components of any deferred quiescent state
are associated with the CPU, which isn't going anywhere until some later
CPU-hotplug operation, which will report any remaining deferred quiescent
states from within the rcu_report_dead() function.

Note also that negative values of ->rcu_read_lock_nesting need not be
considered.  First, these won't show up in exit_rcu() unless there is
a serious bug in RCU, and second, setting ->rcu_read_lock_nesting sets
the state so that the RCU read-side critical section will be exited
normally.

Again, this code has no effect unless there has been some prior bug
that prevents a task from leaving an RCU read-side critical section
before exiting.  Furthermore, there have been no reports of the bug
fixed by this commit appearing in production.  This commit is therefore
absolutely -not- recommended for backporting to -stable.

Reported-by: ABHISHEK DUBEY <dabhishek@iisc.ac.in>
Reported-by: BHARATH Y MOURYA <bharathm@iisc.ac.in>
Reported-by: Aravinda Prasad <aravinda@iisc.ac.in>
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Tested-by: ABHISHEK DUBEY <dabhishek@iisc.ac.in>
2019-03-26 14:37:49 -07:00
Cyrill Gorcunov 18d7e40679 rcu: rcu_qs -- Use raise_softirq_irqoff to not save irqs twice
The rcu_qs is disabling IRQs by self so no need to do the same in raise_softirq
but instead we can save some cycles using raise_softirq_irqoff directly.

CC: Paul E. McKenney <paulmck@linux.ibm.com>
Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-03-26 14:37:49 -07:00
Joel Fernandes (Google) 671a63517c rcu: Avoid unnecessary softirq when system is idle
When there are no callbacks pending on an idle system, I noticed that
RCU softirq is continuously firing. During this the cpu_no_qs is set to
false, and core_needs_qs is set to true indefinitely. This causes
rcu_process_callbacks to be repeatedly called, even though the node
corresponding to the CPU has that CPU's mask bit cleared and the system
is idle. I believe the race is when such mask clearing is done during
idle CPU scan of the quiescent state forcing stage in the kthread
instead of the softirq. Since the rnp mask is cleared, but the flags on
the CPU's rdp are not cleared, the CPU thinks it still needs to report
to core RCU.

Cure this by clearing the core_needs_qs flag when the CPU detects that
its node is already updated which will avoid the unwanted softirq raises
to the benefit of real-time systems.

Test: Ran rcutorture for various tree RCU configs.

Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-03-26 14:37:49 -07:00
Paul E. McKenney e85e6a21b2 rcu: Unconditionally expedite during suspend/hibernate
The rcu_pm_notify() function refuses to switch to/from expedited grace
periods on systems with more than 256 CPUs due to the serialized
initialization of expedited grace periods.  However, expedited grace
periods are now initialized in parallel, removing this concern.
This commit therefore removes the checks from rcu_pm_notify(), so that
expedited grace periods are used unconditionally during suspend/resume
and hibernate/wake operations.

As always, real-time workloads wishing to completely avoid expedited
grace periods can use the rcupdate.rcu_normal= kernel parameter.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-03-26 14:37:49 -07:00
Linus Torvalds 203b6609e0 Merge branch 'perf-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull perf updates from Ingo Molnar:
 "Lots of tooling updates - too many to list, here's a few highlights:

   - Various subcommand updates to 'perf trace', 'perf report', 'perf
     record', 'perf annotate', 'perf script', 'perf test', etc.

   - CPU and NUMA topology and affinity handling improvements,

   - HW tracing and HW support updates:
      - Intel PT updates
      - ARM CoreSight updates
      - vendor HW event updates

   - BPF updates

   - Tons of infrastructure updates, both on the build system and the
     library support side

   - Documentation updates.

   - ... and lots of other changes, see the changelog for details.

  Kernel side updates:

   - Tighten up kprobes blacklist handling, reduce the number of places
     where developers can install a kprobe and hang/crash the system.

   - Fix/enhance vma address filter handling.

   - Various PMU driver updates, small fixes and additions.

   - refcount_t conversions

   - BPF updates

   - error code propagation enhancements

   - misc other changes"

* 'perf-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (238 commits)
  perf script python: Add Python3 support to syscall-counts-by-pid.py
  perf script python: Add Python3 support to syscall-counts.py
  perf script python: Add Python3 support to stat-cpi.py
  perf script python: Add Python3 support to stackcollapse.py
  perf script python: Add Python3 support to sctop.py
  perf script python: Add Python3 support to powerpc-hcalls.py
  perf script python: Add Python3 support to net_dropmonitor.py
  perf script python: Add Python3 support to mem-phys-addr.py
  perf script python: Add Python3 support to failed-syscalls-by-pid.py
  perf script python: Add Python3 support to netdev-times.py
  perf tools: Add perf_exe() helper to find perf binary
  perf script: Handle missing fields with -F +..
  perf data: Add perf_data__open_dir_data function
  perf data: Add perf_data__(create_dir|close_dir) functions
  perf data: Fail check_backup in case of error
  perf data: Make check_backup work over directories
  perf tools: Add rm_rf_perf_data function
  perf tools: Add pattern name checking to rm_rf
  perf tools: Add depth checking to rm_rf
  perf data: Add global path holder
  ...
2019-03-06 07:59:36 -08:00
Linus Torvalds 3717f613f4 Merge branch 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull RCU updates from Ingo Molnar:
 "The main RCU related changes in this cycle were:

   - Additional cleanups after RCU flavor consolidation

   - Grace-period forward-progress cleanups and improvements

   - Documentation updates

   - Miscellaneous fixes

   - spin_is_locked() conversions to lockdep

   - SPDX changes to RCU source and header files

   - SRCU updates

   - Torture-test updates, including nolibc updates and moving nolibc to
     tools/include"

* 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (71 commits)
  locking/locktorture: Convert to SPDX license identifier
  linux/torture: Convert to SPDX license identifier
  torture: Convert to SPDX license identifier
  linux/srcu: Convert to SPDX license identifier
  linux/rcutree: Convert to SPDX license identifier
  linux/rcutiny: Convert to SPDX license identifier
  linux/rcu_sync: Convert to SPDX license identifier
  linux/rcu_segcblist: Convert to SPDX license identifier
  linux/rcupdate: Convert to SPDX license identifier
  linux/rcu_node_tree: Convert to SPDX license identifier
  rcu/update: Convert to SPDX license identifier
  rcu/tree: Convert to SPDX license identifier
  rcu/tiny: Convert to SPDX license identifier
  rcu/sync: Convert to SPDX license identifier
  rcu/srcu: Convert to SPDX license identifier
  rcu/rcutorture: Convert to SPDX license identifier
  rcu/rcu_segcblist: Convert to SPDX license identifier
  rcu/rcuperf: Convert to SPDX license identifier
  rcu/rcu.h: Convert to SPDX license identifier
  RCU/torture.txt: Remove section MODULE PARAMETERS
  ...
2019-03-05 14:49:11 -08:00
Masami Hiramatsu a39f15b964 kprobes: Prohibit probing on RCU debug routine
Since kprobe itself depends on RCU, probing on RCU debug
routine can cause recursive breakpoint bugs.

Prohibit probing on RCU debug routines.

int3
 ->do_int3()
   ->ist_enter()
     ->RCU_LOCKDEP_WARN()
       ->debug_lockdep_rcu_enabled() -> int3

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andrea Righi <righi.andrea@gmail.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/154998807741.31052.11229157537816341591.stgit@devbox
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2019-02-13 08:16:40 +01:00
Masami Hiramatsu c13324a505 x86/kprobes: Prohibit probing on functions before kprobe_int3_handler()
Prohibit probing on the functions called before kprobe_int3_handler()
in do_int3(). More specifically, ftrace_int3_handler(),
poke_int3_handler(), and ist_enter(). And since rcu_nmi_enter() is
called by ist_enter(), it also should be marked as NOKPROBE_SYMBOL.

Since those are handled before kprobe_int3_handler(), probing those
functions can cause a breakpoint recursion and crash the kernel.

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andrea Righi <righi.andrea@gmail.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/154998793571.31052.11301258949601150994.stgit@devbox
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2019-02-13 08:16:39 +01:00
Paul E. McKenney e7ffb4eb9a Merge branches 'doc.2019.01.26a', 'fixes.2019.01.26a', 'sil.2019.01.26a', 'spdx.2019.02.09a', 'srcu.2019.01.26a' and 'torture.2019.01.26a' into HEAD
doc.2019.01.26a:  Documentation updates.
fixes.2019.01.26a:  Miscellaneous fixes.
sil.2019.01.26a:  Removal of a few more spin_is_locked() instances.
spdx.2019.02.09a:  Add SPDX identifiers to RCU files
srcu.2019.01.26a:  SRCU updates.
torture.2019.01.26a: Torture-test updates.
2019-02-09 08:47:52 -08:00
Paul E. McKenney 38b4df649e rcu/update: Convert to SPDX license identifier
Replace the license boiler plate with a SPDX license identifier.
While in the area, update an email address.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
2019-02-09 08:44:27 -08:00
Paul E. McKenney 22e4092531 rcu/tree: Convert to SPDX license identifier
Replace the license boiler plate with a SPDX license identifier.
While in the area, update an email address.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
[ paulmck: Update .h file SPDX comment format per Joe Perches. ]
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
2019-02-09 08:44:10 -08:00
Paul E. McKenney 00de9d7415 rcu/tiny: Convert to SPDX license identifier
Replace the license boiler plate with a SPDX license identifier.
While in the area, update an email address.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
2019-02-09 08:44:05 -08:00
Paul E. McKenney 96b903f5da rcu/sync: Convert to SPDX license identifier
Replace the license boiler plate with a SPDX license identifier.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
2019-02-09 08:43:59 -08:00
Paul E. McKenney e7ee1501cd rcu/srcu: Convert to SPDX license identifier
Replace the license boiler plate with a SPDX license identifier.
While in the area, update an email address.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
2019-02-09 08:43:54 -08:00
Paul E. McKenney 2e24ce8852 rcu/rcutorture: Convert to SPDX license identifier
Replace the license boiler plate with a SPDX license identifier.
While in the area, update an email address.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
2019-02-09 08:43:46 -08:00
Paul E. McKenney eb7935e479 rcu/rcu_segcblist: Convert to SPDX license identifier
Replace the license boiler plate with a SPDX license identifier.
While in the area, update an email address.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
2019-02-09 08:43:40 -08:00
Paul E. McKenney 8bf05ed3ad rcu/rcuperf: Convert to SPDX license identifier
Replace the license boiler plate with a SPDX license identifier.
While in the area, update an email address.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
2019-02-09 08:43:35 -08:00
Paul E. McKenney b5b11890de rcu/rcu.h: Convert to SPDX license identifier
Replace the license boiler plate with a SPDX license identifier.
While in the area, update an email address.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
2019-02-09 08:43:05 -08:00
Paul E. McKenney e838a7d66e rcuperf: Stop abusing IS_ENABLED()
The ever-evolving IS_ENABLED() macro is intended for CONFIG_* Kconfig
options, but rcuperf currently uses it for the decidedly non-CONFIG_*
MODULE macro.  In the spirit of not inviting trouble, this commit
substitutes tried-and-true #ifdef.

Reported-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
2019-01-25 15:37:11 -08:00
Paul E. McKenney 3a6cb58f15 rcutorture: Add grace period after CPU offline
Beyond a certain point in the CPU-hotplug offline process, timers get
stranded on the outgoing CPU, and won't fire until that CPU comes back
online, which might well be never.  This commit therefore adds a hook
in torture_onoff_init() that is invoked from torture_offline(), which
rcutorture uses to occasionally wait for a grace period.  This should
result in failures for RCU implementations that rely on stranded timers
eventually firing in the absence of the CPU coming back online.

Reported-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-01-25 15:37:10 -08:00
Paul E. McKenney cd618d102b rcutorture: Record grace periods in forward-progress histogram
This commit records grace periods in rcutorture's n_launders_hist[]
histogram, thus allowing rcu_torture_fwd_cb_hist() to print out the
elapsed number of grace periods between buckets.  This information
helps to determine whether a lack of forward progress is due to stalled
grace periods on the one hand or due to sluggish callback invocation on
the other.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-01-25 15:37:09 -08:00
Sebastian Andrzej Siewior e81baf4cb1 srcu: Remove srcu_queue_delayed_work_on()
srcu_queue_delayed_work_on() disables preemption (and therefore CPU
hotplug in RCU's case) and then checks based on its own accounting if a
CPU is online. If the CPU is online it uses queue_delayed_work_on()
otherwise it fallbacks to queue_delayed_work().
The problem here is that queue_work() on -RT does not work with disabled
preemption.

queue_work_on() works also on an offlined CPU. queue_delayed_work_on()
has the problem that it is possible to program a timer on an offlined
CPU. This timer will fire once the CPU is online again. But until then,
the timer remains programmed and nothing will happen.

Add a local timer which will fire (as requested per delay) on the local
CPU and then enqueue the work on the specific CPU.

RCUtorture testing with SRCU-P for 24h showed no problems.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-01-25 15:36:42 -08:00
Paul E. McKenney c2d8089de7 rcu: Fix obsolete DYNTICK_IRQ_NONIDLE comment
This commit updates the DYNTICK_IRQ_NONIDLE header comment to remove
the obsolete commentary about unmatched rcu_irq_{enter,exit}().

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-01-25 15:35:24 -08:00
Paul E. McKenney 39abefe743 rcu: Repair rcu_nmi_exit() docbook header
This commit removes the "@irq" argument from the rcu_nmi_exit() docbook
header, given that this function now has no arguments.

Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-01-25 15:35:23 -08:00
Paul E. McKenney 5a0874c1d1 rcu: Remove preemption disabling from expedited CPU selection
It turns out that it is queue_delayed_work_on() rather than
queue_work_on() that has difficulties when used concurrently with
CPU-hotplug removal operations.  It is therefore unnecessary to protect
CPU identification and queue_work_on() with preempt_disable().

This commit therefore removes the preempt_disable() and preempt_enable()
from sync_rcu_exp_select_cpus(), which has the further benefit of reducing
the number of changes that must be maintained in the -rt patchset.

Reported-by: Thomas Gleixner <tglx@linutronix.de>
Reported-by: Sebastian Siewior <bigeasy@linutronix.de>
Suggested-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-01-25 15:35:23 -08:00
Paul E. McKenney fb60e533be rcu: Rename rcu_process_callbacks() to rcu_core() for Tree RCU
Although the name rcu_process_callbacks() still makes sense for Tiny
RCU, where most of what it does is invoke callbacks, it no longer makes
much sense for Tree RCU, especially given that the actually callback
invocation is relegated to rcu_do_batch(), or, for no-CBs CPUs, to the
rcuo kthreads.  Especially in the latter case, rcu_process_callbacks()
has very little to do with actual callbacks.  A better description of
this function is that it performs RCU's core processing.

This commit therefore changes the name of Tree RCU's rcu_process_callbacks()
function to rcu_core(), which also has the virtue of being consistent with
the existing invoke_rcu_core() function.

While in the area, the header comment is reworked.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-01-25 15:35:22 -08:00
Paul E. McKenney c98cac603f rcu: Rename rcu_check_callbacks() to rcu_sched_clock_irq()
The name rcu_check_callbacks() arguably made sense back in the early
2000s when RCU was quite a bit simpler than it is today, but it has
become quite misleading, especially with the advent of dyntick-idle
and NO_HZ_FULL.  The rcu_check_callbacks() function is RCU's hook into
the scheduling-clock interrupt, and is now but one of many ways that
callbacks get promoted to invocable state.

This commit therefore changes the name to rcu_sched_clock_irq(),
which is the same number of characters and clearly indicates this
function's relation to the rest of the Linux kernel.  In addition, for
the sake of consistency, rcu_flavor_check_callbacks() is also renamed
to rcu_flavor_sched_clock_irq().

While in the area, the header comments for both functions are reworked.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-01-25 15:35:21 -08:00
Paul E. McKenney 7a968bb26a Merge branches 'consolidate.2019.01.26a' and 'fwd.2019.01.26a' into HEAD
consolidate.2019.01.26a: RCU flavor consolidation cleanups.
fwd.2019.01.26a: RCU grace-period forward-progress fixes.
2019-01-25 15:32:01 -08:00
Zhang, Jun 13dc7d0c7a rcu: Prevent needless ->gp_seq_needed update in __note_gp_changes()
Currently, __note_gp_changes() checks to see if the rcu_node structure's
->gp_seq_needed is greater than or equal to that of the rcu_data
structure, and if so, updates the rcu_data structure's ->gp_seq_needed
field.  This results in a useless store in the case where the two fields
are equal.

This commit therefore carries out this store only in the case where the
rcu_node structure's ->gp_seq_needed is strictly greater than that of
the rcu_data structure.

Signed-off-by: "Zhang, Jun" <jun.zhang@intel.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Link: https://lkml.kernel.org/r/88DC34334CA3444C85D647DBFA962C2735AD5F77@SHSMSX104.ccr.corp.intel.com
2019-01-25 15:30:00 -08:00
Zhang, Jun 1d1f898df6 rcu: Do RCU GP kthread self-wakeup from softirq and interrupt
The rcu_gp_kthread_wake() function is invoked when it might be necessary
to wake the RCU grace-period kthread.  Because self-wakeups are normally
a useless waste of CPU cycles, if rcu_gp_kthread_wake() is invoked from
this kthread, it naturally refuses to do the wakeup.

Unfortunately, natural though it might be, this heuristic fails when
rcu_gp_kthread_wake() is invoked from an interrupt or softirq handler
that interrupted the grace-period kthread just after the final check of
the wait-event condition but just before the schedule() call.  In this
case, a wakeup is required, even though the call to rcu_gp_kthread_wake()
is within the RCU grace-period kthread's context.  Failing to provide
this wakeup can result in grace periods failing to start, which in turn
results in out-of-memory conditions.

This race window is quite narrow, but it actually did happen during real
testing.  It would of course need to be fixed even if it was strictly
theoretical in nature.

This patch does not Cc stable because it does not apply cleanly to
earlier kernel versions.

Fixes: 48a7639ce8 ("rcu: Make callers awaken grace-period kthread")
Reported-by: "He, Bo" <bo.he@intel.com>
Co-developed-by: "Zhang, Jun" <jun.zhang@intel.com>
Co-developed-by: "He, Bo" <bo.he@intel.com>
Co-developed-by: "xiao, jin" <jin.xiao@intel.com>
Co-developed-by: Bai, Jie A <jie.a.bai@intel.com>
Signed-off: "Zhang, Jun" <jun.zhang@intel.com>
Signed-off: "He, Bo" <bo.he@intel.com>
Signed-off: "xiao, jin" <jin.xiao@intel.com>
Signed-off: Bai, Jie A <jie.a.bai@intel.com>
Signed-off-by: "Zhang, Jun" <jun.zhang@intel.com>
[ paulmck: Switch from !in_softirq() to "!in_interrupt() &&
  !in_serving_softirq() to avoid redundant wakeups and to also handle the
  interrupt-handler scenario as well as the softirq-handler scenario that
  actually occurred in testing. ]
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Link: https://lkml.kernel.org/r/CD6925E8781EFD4D8E11882D20FC406D52A11F61@SHSMSX104.ccr.corp.intel.com
2019-01-25 15:29:59 -08:00
Paul E. McKenney 2ccaff10f7 rcu: Add sysrq rcu_node-dump capability
Life is hard if RCU manages to get stuck without triggering RCU CPU
stall warnings or triggering the rcu_check_gp_start_stall() checks
for failing to start a grace period.  This commit therefore adds a
boot-time-selectable sysrq key (commandeering "y") that allows manually
dumping Tree RCU state.  The new rcutree.sysrq_rcu kernel boot parameter
must be set for this sysrq to be available.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-01-25 15:29:59 -08:00
Paul E. McKenney 3b6505fd8e rcu: Protect rcu_check_gp_kthread_starvation() access to ->gp_flags
The rcu_check_gp_kthread_starvation() function can be invoked without
holding locks, so the access to the rcu_state structure's ->gp_flags
field must be protected with READ_ONCE().  This commit therefore adds
this protection.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-01-25 15:29:58 -08:00
Paul E. McKenney fd897573fa rcu: Improve diagnostics for failed RCU grace-period start
If a grace period fails to start (for example, because you commented
out the last two lines of rcu_accelerate_cbs_unlocked()), rcu_core()
will invoke rcu_check_gp_start_stall(), which will notice and complain.
However, this complaint is lacking crucial debugging information such
as when the last wakeup executed and what the value of ->gp_seq was at
that time.  This commit therefore removes the current pr_alert() from
rcu_check_gp_start_stall(), instead invoking show_rcu_gp_kthreads(),
which has been updated to print the needed information, which is collected
by rcu_gp_kthread_wake().

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-01-25 15:29:57 -08:00
Paul E. McKenney a9fefdb257 rcu: Update NOCB comments
This commit updates a few obsolete comments in the RCU callback-offload
code.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-01-25 15:29:57 -08:00
Paul E. McKenney b2c1955b88 rcu: Remove unused rcu_cpu_kthread_cpu per-CPU variable
The rcu_cpu_kthread_cpu used to provide debugfs information, but is no
longer used.  This commit therefore removes it.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-01-25 15:29:56 -08:00
Paul E. McKenney f7e972ee12 rcu: Move rcu_cpu_has_work to rcu_data structure
Given that RCU has a perfectly good per-CPU rcu_data structure, most
per-CPU quantities should be stored there.

This commit therefore moves the rcu_cpu_has_work per-CPU variable to
the rcu_data structure.  This also makes this variable unconditionally
present, which should be acceptable given the memory reduction due to the
RCU flavor consolidation and also due to simplifications this will enable.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-01-25 15:29:56 -08:00
Paul E. McKenney 8b4d0f4858 rcu: Remove unused rcu_cpu_kthread_loops per-CPU variable
The rcu_cpu_kthread_loops variable used to provide debugfs information,
but is no longer used.  This commit therefore removes it.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-01-25 15:29:55 -08:00
Paul E. McKenney 6ffdde28b7 rcu: Move rcu_cpu_kthread_status to rcu_data structure
Given that RCU has a perfectly good per-CPU rcu_data structure, most
per-CPU quantities should be stored there.

This commit therefore moves the rcu_cpu_kthread_status per-CPU variable
to the rcu_data structure.  This also makes this variable unconditionally
present, which should be acceptable given the memory reduction due to the
RCU flavor consolidation and also due to simplifications this will enable.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-01-25 15:29:54 -08:00
Paul E. McKenney 37f62d7cf0 rcu: Move rcu_cpu_kthread_task to rcu_data structure
Given that RCU has a perfectly good per-CPU rcu_data structure, most
per-CPU quantities should be stored there.

This commit therefore moves the rcu_cpu_kthread_task per-CPU variable to
the rcu_data structure.  This also makes this variable unconditionally
present, which should be acceptable given the memory reduction due to the
RCU flavor consolidation and also due to simplifications this will enable.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-01-25 15:29:53 -08:00
Paul E. McKenney 9cf422a8e7 rcu: Accommodate zero jiffies_till_first_fqs and kthread kicking
It is perfectly fine to set the rcutree.jiffies_till_first_fqs boot
parameter to zero, in fact, this can be useful on specialty systems that
usually have at least one idle CPU and that need fast grace periods.
This is because this setting causes the RCU grace-period kthread to
scan for idle threads immediately after grace-period initialization,
as opposed to waiting several jiffies to do so.

It is also perfectly fine to set the rcutree.rcu_kick_kthreads kernel
parameter, which gives the RCU grace-period kthread an extra wakeup
if it doesn't make progress for a period of three times the setting of
the rcutree.jiffies_till_first_fqs boot parameter.  This is of course
problematic when the value of this parameter is zero, as it can result
in unnecessary wakeup IPIs along with unnecessary WARN_ONCE() invocations.

This commit therefore defers kthread kicking for at least two jiffies,
regardless of the setting of rcutree.jiffies_till_first_fqs.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-01-25 15:29:53 -08:00
Paul E. McKenney 260e1e4fd8 rcu: Discard separate per-CPU callback counts
Back when there were multiple flavors of RCU, it was necessary to
separately count lazy and non-lazy callbacks for each CPU.  These counts
were used in CONFIG_RCU_FAST_NO_HZ kernels to determine how long a newly
idle CPU should be allowed to sleep before handling its RCU callbacks.
But now that there is only one flavor, the callback counts for a given
CPU's sole rcu_data structure are the counts for that CPU.

This commit therefore removes the rcu_data structure's ->nonlazy_posted
and ->nonlazy_posted_snap fields, the rcu_idle_count_callbacks_posted()
and rcu_cpu_has_callbacks() functions, repurposes the rcu_data structure's
->all_lazy field to record the laziness state at the beginning of the
latest idle sojourn, and modifies CONFIG_RCU_FAST_NO_HZ RCU CPU stall
warnings accordingly.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-01-25 15:28:30 -08:00
Paul E. McKenney 8923072664 rcu: Inline _synchronize_rcu_expedited() into synchronize_rcu_expedited()
Now that _synchronize_rcu_expedited() has only one caller, and given that
this is a tail call, this commit inlines _synchronize_rcu_expedited()
into synchronize_rcu_expedited().

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-01-25 15:28:29 -08:00
Paul E. McKenney e5bc3af773 rcu: Consolidate PREEMPT and !PREEMPT synchronize_rcu()
Now that rcu_blocking_is_gp() makes the correct immediate-return
decision for both PREEMPT and !PREEMPT, a single implementation of
synchronize_rcu() will work correctly under both configurations.
This commit therefore eliminates a few lines of code by consolidating
the two implementations of synchronize_rcu().

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-01-25 15:28:28 -08:00
Paul E. McKenney 3cd4ca47aa rcu: Consolidate PREEMPT and !PREEMPT synchronize_rcu_expedited()
The CONFIG_PREEMPT=n and CONFIG_PREEMPT=y implementations of
synchronize_rcu_expedited() are quite similar, and with small
modifications to rcu_blocking_is_gp() can be made identical.  This commit
therefore makes this change in order to save a few lines of code and to
reduce the amount of duplicate code.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-01-25 15:28:27 -08:00
Paul E. McKenney 142d106d5e rcu: Determine expedited-GP IPI handler at build time
Back when there could be multiple RCU flavors running in the same kernel
at the same time, it was necessary to specify the expedited grace-period
IPI handler at runtime.  Now that there is only one RCU flavor, the
IPI handler can be determined at build time.  There is therefore no
longer any reason for the RCU-preempt and RCU-sched IPI handlers to
have different names, nor is there any reason to pass these handlers in
function arguments and in the data structures enclosing workqueues.

This commit therefore makes all these changes, pushing the specification
of the expedited grace-period IPI handler down to the point of use.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-01-25 15:28:27 -08:00
Paul E. McKenney c46f497a61 rcu: Inline rcu_kthread_do_work() into its sole remaining caller
The rcu_kthread_do_work() function has a single-line body and only one
remaining caller.  This commit therefore saves a few lines of code by
inlining rcu_kthread_do_work() into its sole remaining caller.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-01-25 15:28:25 -08:00
Paul E. McKenney c97058d033 rcu: Eliminate RCU_BH_FLAVOR and RCU_SCHED_FLAVOR
Now that the RCU flavors have been consolidated, RCU_BH_FLAVOR and
RCU_SCHED_FLAVOR are no longer used.  This commit therefore saves a
few lines by removing them.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-01-25 15:28:25 -08:00
Paul E. McKenney cd920e5a34 rcu: Inline force_quiescent_state() into rcu_force_quiescent_state()
Given that rcu_force_quiescent_state() is a simple wrapper around
force_quiescent_state(), this commit saves a few lines of code by
inlining force_quiescent_state() into rcu_force_quiescent_state(),
and changing all references to force_quiescent_state() to instead
invoke rcu_force_quiescent_state().

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-01-25 15:28:24 -08:00
Paul E. McKenney 1de462ed85 rcu: Make expedited IPI handler return after handling critical section
During expedited RCU grace-period initialization, IPIs are sent to
all non-idle online CPUs.  The IPI handler checks to see if the CPU is
in quiescent state, reporting one if so.  This handler looks at three
different cases: (1) The CPU is not in an rcu_read_lock()-based critical
section, (2) The CPU is in the process of exiting an rcu_read_lock()-based
critical section, and (3) The CPU is in an rcu_read_lock()-based critical
section.  In case (2), execution falls through into case (3).

This is harmless from a functionality viewpoint, but can result in
needless overhead during an improbable corner case.  This commit therefore
adds the "return" statement needed to prevent fall-through.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-01-25 15:28:24 -08:00
Paul E. McKenney ad368d15b0 rcu: Rename and comment changes due to only one rcuo kthread per CPU
Given RCU flavor consolidation, the name rcu_spawn_all_nocb_kthreads()
is quite misleading.  It no longer ever creates more than one kthread,
and it does so only for the specified CPU.  This commit therefore changes
this name to the more descriptive rcu_spawn_cpu_nocb_kthread(), and also
fixes up a similar issue in its header comment while in the area.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-01-25 15:28:23 -08:00
Paul E. McKenney a4cffdad73 time: Move CONTEXT_TRACKING to kernel/time/Kconfig
Both CONTEXT_TRACKING and CONTEXT_TRACKING_FORCE are currently defined
in kernel/rcu/kconfig, which might have made sense at some point, but
no longer does given that RCU refers to neither of these Kconfig options.

Therefore move them to kernel/time/Kconfig, where the rest of the
NO_HZ_FULL Kconfig options live.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Link: https://lkml.kernel.org/r/20181220170525.GA12579@linux.ibm.com
2019-01-15 11:16:41 +01:00
Paul E. McKenney 5ac7cdc298 rcutorture: Don't do busted forward-progress testing
The "busted" rcutorture type is an intentionally broken implementation
of RCU.  Doing forward-progress testing on this implementation is not
particularly meaningful on the one hand and can result in fatal abuse
of the memory allocator on the other.  This commit therefore disables
forward-progress testing of the "busted" rcutorture type.

Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2018-12-01 12:45:42 -08:00
Paul E. McKenney 2e57bf97a6 rcutorture: Use 100ms buckets for forward-progress callback histograms
This commit narrows the scope of each bucket of the forward-progress
callback-invocation histograms from one second to 100 milliseconds, which
aids debugging of forward-progress problems by making shorter-duration
callback-invocation stalls visible.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2018-12-01 12:45:41 -08:00
Paul E. McKenney 2667ccce93 rcutorture: Recover from OOM during forward-progress tests
This commit causes the OOM handler to do rcu_barrier() calls and to
free up forward-progress callbacks in order to recover from OOM events.
The current test is terminated, but subsequent forward-progress tests can
proceed.  This allows a long test to result in multiple forward-progress
failures, greatly reducing the required testing time.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2018-12-01 12:45:41 -08:00
Paul E. McKenney 73d665b141 rcutorture: Print forward-progress test age upon failure
This commit prints the age of the forward-progress test in jiffies,
in order to allow better interpretation of the callback-invocation
histograms.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2018-12-01 12:45:40 -08:00
Paul E. McKenney c51d7b5e6c rcutorture: Print time since GP end upon forward-progress failure
If rcutorture's forward-progress tests fail while a grace period is not
in progress, it is useful to print the time since the last grace period
ended as a way to detect failure to launch a new grace period.  This
commit therefore makes this change.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2018-12-01 12:45:40 -08:00
Paul E. McKenney 1a682754c7 rcutorture: Print histogram of CB invocation at OOM time
One reason why a forward-progress test might fail would be if something
prevented or delayed callback invocation.  This commit therefore adds a
callback-invocation histogram printout when OOM is reported to rcutorture.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2018-12-01 12:45:39 -08:00
Paul E. McKenney 8dd3b54689 rcutorture: Print GP age upon forward-progress failure
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2018-12-01 12:45:38 -08:00
Paul E. McKenney bfcfcffc5f rcu: Print per-CPU callback counts for forward-progress failures
This commit prints out the non-zero per-CPU callback counts when a
forware-progress error (OOM event) occurs.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
[ paulmck: Fix a pair of uninitialized locals spotted by kbuild test robot. ]
2018-12-01 12:45:38 -08:00
Paul E. McKenney 903ee83d91 rcu: Account for nocb-CPU callback counts in RCU CPU stall warnings
The RCU CPU stall warnings print an estimate of the total number of
RCU callbacks queued in the system, but this estimate leaves out
the callbacks queued for nocbs CPUs.  This commit therefore introduces
rcu_get_n_cbs_cpu(), which gives an accurate callback estimate for
both nocbs and normal CPUs, and uses this new function as needed.

This commit also introduces a rcu_get_n_cbs_nocb_cpu() helper function
that returns the number of callbacks for nocbs CPUs or zero otherwise,
and also uses this function in place of direct access to ->nocb_q_count
while in the area (fewer characters, you see).

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2018-12-01 12:45:37 -08:00
Paul E. McKenney e0aff97355 rcutorture: Dump grace-period diagnostics upon forward-progress OOM
This commit adds an OOM notifier during rcutorture forward-progress
testing.  If this notifier is invoked, it dumps out some grace-period
state to help debug the forward-progress problem.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2018-12-01 12:45:36 -08:00
Paul E. McKenney 61670adcb4 rcutorture: Prepare for asynchronous access to rcu_fwd_startat
Because rcutorture's forward-progress checking will trigger from an
OOM notifier, this notifier will introduce asynchronous concurrent
access to the rcu_fwd_startat variable.  This commit therefore prepares
for this by converting updates to WRITE_ONCE().

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2018-12-01 12:45:35 -08:00
Paul E. McKenney 5ab7ab8362 rcutorture: Affinity forward-progress test to avoid housekeeping CPUs
This commit affinities the forward-progress tests to avoid hogging a
housekeeping CPU on the theory that the offloaded callbacks will be
running on those housekeeping CPUs.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
[ paulmck: Fix NULL-pointer issue located by kbuild test robot. ]
Tested-by: Rong Chen <rong.a.chen@intel.com>
2018-12-01 12:45:34 -08:00
Paul E. McKenney 6b3de7a172 rcutorture: Break up too-long rcu_torture_fwd_prog() function
This commit splits rcu_torture_fwd_prog_nr() and rcu_torture_fwd_prog_cr()
functions out of rcu_torture_fwd_prog() in order to reduce indentation
pain and because rcu_torture_fwd_prog() was getting a bit too long.
In addition, this will enable easier conditional execution of the
rcu_torture_fwd_prog_cr() function, which can give false-positive
failures in some NO_HZ_FULL configurations due to overloading the
housekeeping CPUs.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-12-01 12:45:34 -08:00
Paul E. McKenney fc6f9c5778 rcutorture: Remove cbflood facility
Now that the forward-progress code does a full-bore continuous callback
flood lasting multiple seconds, there is little point in also posting a
mere 60,000 callbacks every second or so.  This commit therefore removes
the old cbflood testing.  Over time, it may be desirable to concurrently
do full-bore continuous callback floods on all CPUs simultaneously, but
one dragon at a time.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-12-01 12:45:33 -08:00
Paul E. McKenney 4871848531 rcutorture: Add call_rcu() flooding forward-progress tests
This commit adds a call_rcu() flooding loop to the forward-progress test.
This emulates tight userspace loops that force call_rcu() invocations,
for example, the infamous loop containing close(open()) that instigated
the addition of blimit.  If RCU does not make sufficient forward progress
in invoking the resulting flood of callbacks, rcutorture emits a warning.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-12-01 12:45:32 -08:00
Paul E. McKenney eaaf055f27 Merge branches 'bug.2018.11.12a', 'consolidate.2018.12.01a', 'doc.2018.11.12a', 'fixes.2018.11.12a', 'initrd.2018.11.08b', 'sil.2018.11.12a' and 'srcu.2018.11.27a' into HEAD
bug.2018.11.12a:  Get rid of BUG_ON() and friends
consolidate.2018.12.01a:  Continued RCU flavor-consolidation cleanup
doc.2018.11.12a:  Documentation updates
fixes.2018.11.12a:  Miscellaneous fixes
initrd.2018.11.08b:  Automate creation of rcutorture initrd
sil.2018.11.12a:  Remove more spin_unlock_wait() calls
2018-12-01 12:43:16 -08:00
Paul E. McKenney aacb5d91ab srcu: Use "ssp" instead of "sp" for srcu_struct pointer
In RCU, the distinction between "rsp", "rnp", and "rdp" has served well
for a great many years, but in SRCU, "sp" vs. "sdp" has proven confusing.
This commit therefore renames SRCU's "sp" pointers to "ssp", so that there
is "ssp" for srcu_struct pointer, "snp" for srcu_node pointer, and "sdp"
for srcu_data pointer.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2018-11-27 09:24:17 -08:00
Dennis Krein eb4c238227 srcu: Lock srcu_data structure in srcu_gp_start()
The srcu_gp_start() function is called with the srcu_struct structure's
->lock held, but not with the srcu_data structure's ->lock.  This is
problematic because this function accesses and updates the srcu_data
structure's ->srcu_cblist, which is protected by that lock.  Failing to
hold this lock can result in corruption of the SRCU callback lists,
which in turn can result in arbitrarily bad results.

This commit therefore makes srcu_gp_start() acquire the srcu_data
structure's ->lock across the calls to rcu_segcblist_advance() and
rcu_segcblist_accelerate(), thus preventing this corruption.

Reported-by: Bart Van Assche <bvanassche@acm.org>
Reported-by: Christoph Hellwig <hch@infradead.org>
Reported-by: Sebastian Kuzminsky <seb.kuzminsky@gmail.com>
Signed-off-by: Dennis Krein <Dennis.Krein@netapp.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Tested-by: Dennis Krein <Dennis.Krein@netapp.com>
Cc: <stable@vger.kernel.org> # 4.16.x
2018-11-27 09:23:57 -08:00
Paul E. McKenney 5f1a6ef374 rcu: Avoid signed integer overflow in rcu_preempt_deferred_qs()
Subtracting INT_MIN can be interpreted as unconditional signed integer
overflow, which according to the C standard is undefined behavior.
Therefore, kernel build arguments notwithstanding, it would be good to
future-proof the code.  This commit therefore substitutes INT_MAX for
INT_MIN in order to avoid undefined behavior.

While in the neighborhood, this commit also creates some meaningful names
for INT_MAX and friends in order to improve readability, as suggested
by Joel Fernandes.

Reported-by: Ran Rozenstein <ranro@mellanox.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2018-11-12 09:03:59 -08:00
Paul E. McKenney 117f683c6e rcu: Replace this_cpu_ptr() with __this_cpu_read()
Because __this_cpu_read() can be lighter weight than equivalent uses of
this_cpu_ptr(), this commit replaces the latter with the former.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2018-11-12 09:03:59 -08:00
Paul E. McKenney 05f415715c rcu: Speed up expedited GPs when interrupting RCU reader
In PREEMPT kernels, an expedited grace period might send an IPI to a
CPU that is executing an RCU read-side critical section.  In that case,
it would be nice if the rcu_read_unlock() directly interacted with the
RCU core code to immediately report the quiescent state.  And this does
happen in the case where the reader has been preempted.  But it would
also be a nice performance optimization if immediate reporting also
happened in the preemption-free case.

This commit therefore adds an ->exp_hint field to the task_struct structure's
->rcu_read_unlock_special field.  The IPI handler sets this hint when
it has interrupted an RCU read-side critical section, and this causes
the outermost rcu_read_unlock() call to invoke rcu_read_unlock_special(),
which, if preemption is enabled, reports the quiescent state immediately.
If preemption is disabled, then the report is required to be deferred
until preemption (or bottom halves or interrupts or whatever) is re-enabled.

Because this is a hint, it does nothing for more complicated cases.  For
example, if the IPI interrupts an RCU reader, but interrupts are disabled
across the rcu_read_unlock(), but another rcu_read_lock() is executed
before interrupts are re-enabled, the hint will already have been cleared.
If you do crazy things like this, reporting will be deferred until some
later RCU_SOFTIRQ handler, context switch, cond_resched(), or similar.

Reported-by: Joel Fernandes <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Acked-by: Joel Fernandes (Google) <joel@joelfernandes.org>
2018-11-12 09:03:59 -08:00
Paul E. McKenney 0a89e5a402 rcu: Trace end of grace period before end of grace period
Currently, rcu_gp_cleanup() traces the end of the old grace period after
the old grace period has officially ended.  This might make intuitive
sense, but it also makes for confusing event-trace output because the
"end" trace displays not the old but instead the new grace-period number.
This commit therefore traces the end of an old grace period just before
that grace period officially ends.

Reported-by: Aravinda Prasad <aravinda@linux.vnet.ibm.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2018-11-12 09:03:59 -08:00
Zhouyi Zhou 2320bda26d rcu: Adjust the comment of function rcu_is_watching
Because RCU avoids interrupting idle CPUs, rcu_is_watching() is used to
test whether or not it is currently legal to run RCU read-side critical
sections on this CPU.  However, the first sentence and last sentences
of current comment for rcu_is_watching have opposite meaning of what
is expected.  This commit therefore fixes this header comment.

Signed-off-by: Zhouyi Zhou <zhouzhouyi@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2018-11-12 09:03:59 -08:00
Paul E. McKenney c669c014d1 rcu: Add jiffies-since-GP-activity to show_rcu_gp_kthreads()
This commit adds a printout of the number of jiffies since the last time
that the RCU grace-period kthread did any processing.  This can be useful
when tracking down forward-progress issues.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2018-11-12 09:03:59 -08:00
Paul E. McKenney 691960197e rcu: Add state name to show_rcu_gp_kthreads() output
This commit adds the name of the RCU grace-period state to
the show_rcu_gp_kthreads() output in order to ease debugging.
This commit also moves gp_state_getname() up in the code so that
show_rcu_gp_kthreads() can use it.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2018-11-12 09:03:59 -08:00
Paul E. McKenney 791416c471 rcu: Parameterize rcu_check_gp_start_stall()
In order to debug forward-progress stalls, it is necessary to check
for excessively delayed grace-period starts.  This is currently done
for RCU CPU stall warnings by rcu_check_gp_start_stall(), which checks
to see if the start of a requested grace period has been delayed by an
RCU CPU stall warning period.  Because rcutorture will need to check
for the time consumed by an RCU forward-progress delay, this commit
promotes gpssdelay from a local variable to a formal parameter.  It is
not necessary to export rcu_check_gp_start_stall() because rcutorture
will access it via a wrapper function.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2018-11-12 09:03:59 -08:00
Paul E. McKenney b3c1d9ec7c rcu: Avoid double multiply by HZ
The rcu_check_gp_start_stall() function multiplies the return value
from rcu_jiffies_till_stall_check() by HZ, but the units are already
in jiffies.  This commit therefore avoids the need for introduction of
a jiffies-squared unit by removing the extraneous multiplication.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2018-11-12 09:03:59 -08:00
Paul E. McKenney f0ad56e876 rcu: Eliminate BUG_ON() for kernel/rcu/update.c
The update.c file has a number of calls to BUG_ON(), which panics the
kernel, which is not a good strategy for devices (like embedded) that
don't have a way to capture console output.  This commit therefore
converts these BUG_ON() calls to WARN_ON_ONCE() and WARN_ONCE().

Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2018-11-12 08:15:59 -08:00
Paul E. McKenney 9213784b48 rcu: Eliminate BUG_ON() for kernel/rcu/tree_plugin.h
The tree_plugin.h file has a number of calls to BUG_ON(), which panics
the kernel, which is not a good strategy for devices (like embedded)
that don't have a way to capture console output.  This commit therefore
converts these BUG_ON() calls to WARN_ON_ONCE() and WARN_ONCE().

Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
[ paulmck: Fix typo: s/rcuo/rcub/. ]
2018-11-12 08:15:16 -08:00
Paul E. McKenney 9cac83a57e rcu: Stop expedited grace periods from relying on stop-machine
The CPU-selection code in sync_rcu_exp_select_cpus() disables preemption
to prevent the cpu_online_mask from changing.  However, this relies on
the stop-machine mechanism in the CPU-hotplug offline code, which is not
desirable (it would be good to someday remove the stop-machine mechanism).

This commit therefore instead uses the relevant leaf rcu_node structure's
->ffmask, which has a bit set for all CPUs that are fully functional.
A given CPU's bit is cleared very early during offline processing by
rcutree_offline_cpu() and set very late during online processing by
rcutree_online_cpu().  Therefore, if a CPU's bit is set in this mask, and
preemption is disabled, we have to be before the synchronize_sched() in
the CPU-hotplug offline code, which means that the CPU is guaranteed to be
workqueue-ready throughout the duration of the enclosing preempt_disable()
region of code.

This also has the side-effect of using WORK_CPU_UNBOUND if all the CPUs for
this leaf rcu_node structure are offline, which is an acceptable difference
in behavior.

Reported-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-11-11 11:23:01 -08:00
Paul E. McKenney 0607ba8403 srcu: Prevent __call_srcu() counter wrap with read-side critical section
Ever since cdf7abc461 ("srcu: Allow use of Tiny/Tree SRCU from
both process and interrupt context"), it has been permissible
to use SRCU read-side critical sections in interrupt context.
This allows __call_srcu() to use SRCU read-side critical sections to
prevent a new SRCU grace period from ending before the call to either
srcu_funnel_gp_start() or srcu_funnel_exp_start completes, thus preventing
SRCU grace-period counter overflow during that time.

Note that this does not permit removal of the counter-wrap checks in
srcu_gp_end().  These check are necessary to handle the case where
a given CPU does not interact at all with SRCU for an extended time
period.

This commit therefore adds an SRCU read-side critical section to
__call_srcu() in order to prevent grace period counter wrap during
the funnel-locking process.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-11-08 21:54:14 -08:00
Paul E. McKenney d3ff3891b2 rcu: Consolidate the RCU update functions invoked by sync.c
This commit retains all the various gp_ops[] entries, but makes their
update functions all be synchronize_rcu(), call_rcu() and rcu_barrier().
The read-side checks remain consistent with the various RCU flavors,
which still exist on the read side.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
2018-11-08 21:43:20 -08:00
Paul E. McKenney 309ba859b9 rcu: Eliminate synchronize_rcu_mult()
Now that synchronize_rcu() waits for both RCU read-side critical
sections and preempt-disabled regions of code, the sole caller of
synchronize_rcu_mult() can be replaced by synchronize_rcu().
This patch makes this change and removes synchronize_rcu_mult().
Note that _wait_rcu_gp() still supports synchronize_rcu_mult(),
and thus might be simplified in the future to take only take
a single call_rcu() function rather than the current list of them.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-11-08 21:43:20 -08:00
Joel Fernandes (Google) adbccddb4a rcu: Fix rcu_{node,data} comments about gp_seq_needed
Recent changes have removed the old ->gp_seq_needed field from the
rcu_state structure, which in turn obsoleted a couple of comments in
the rcu_node and rcu_data structures.  This commit therefore updates
these comments accordingly.

Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Cc: <kernel-team@android.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2018-11-08 21:43:20 -08:00
Joel Fernandes (Google) 75a8f72245 rcu: Remove unused rcu_state externs
The rcu_bh_state and rcu_sched_state variables were removed during the
RCU flavor consolidations, but external declarations remain in tree.h.
This commit therefore removes these obsolete declarations.

Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Cc: <kernel-team@android.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2018-11-08 21:43:20 -08:00
Paul E. McKenney 08543bda42 rcu: Eliminate BUG_ON() for kernel/rcu/tree.c
The tree.c file has a number of calls to BUG_ON(), which panics the
kernel, which is not a good strategy for devices (like embedded) that
don't have a way to capture console output.  This commit therefore
converts these BUG_ON() calls to WARN_ON_ONCE() and WARN_ONCE().

Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2018-11-08 21:41:57 -08:00
Paul E. McKenney 042d4c70a2 rcu: Eliminate BUG_ON() for sync.c
The sync.c file has a number of calls to BUG_ON(), which panics the
kernel, which is not a good strategy for devices (like embedded) that
don't have a way to capture console output.  This commit therefore
changes these BUG_ON() calls to WARN_ON_ONCE(), but does so quite naively.

Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
2018-11-08 21:41:57 -08:00
Paul E. McKenney b56ada1209 Merge branches 'doc.2018.08.30a', 'dynticks.2018.08.30b', 'srcu.2018.08.30b' and 'torture.2018.08.29a' into HEAD
doc.2018.08.30a: Documentation updates
dynticks.2018.08.30b: RCU flavor consolidation updates and cleanups
srcu.2018.08.30b: SRCU updates
torture.2018.08.29a: Torture-test updates
2018-08-30 16:12:53 -07:00
Paul E. McKenney 4e6ea4ef56 srcu: Make early-boot call_srcu() reuse workqueue lists
Allocating a list_head structure that is almost never used, and, when
used, is used only during early boot (rcu_init() and earlier), is a bit
wasteful.  This commit therefore eliminates that list_head in favor of
the one in the work_struct structure.  This is safe because the work_struct
structure cannot be used until after rcu_init() returns.

Reported-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Tested-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
2018-08-30 16:10:49 -07:00
Paul E. McKenney e0fcba9ac0 srcu: Make call_srcu() available during very early boot
Event tracing is moving to SRCU in order to take advantage of the fact
that SRCU may be safely used from idle and even offline CPUs.  However,
event tracing can invoke call_srcu() very early in the boot process,
even before workqueue_init_early() is invoked (let alone rcu_init()).
Therefore, call_srcu()'s attempts to queue work fail miserably.

This commit therefore detects this situation, and refrains from attempting
to queue work before rcu_init() time, but does everything else that it
would have done, and in addition, adds the srcu_struct to a global list.
The rcu_init() function now invokes a new srcu_init() function, which
is empty if CONFIG_SRCU=n.  Otherwise, srcu_init() queues work for
each srcu_struct on the list.  This all happens early enough in boot
that there is but a single CPU with interrupts disabled, which allows
synchronization to be dispensed with.

Of course, the queued work won't actually be invoked until after
workqueue_init() is invoked, which happens shortly after the scheduler
is up and running.  This means that although call_srcu() may be invoked
any time after per-CPU variables have been set up, there is still a very
narrow window when synchronize_srcu() won't work, and this window
extends from the time that the scheduler starts until the time that
workqueue_init() returns.  This can be fixed in a manner similar to
the fix for synchronize_rcu_expedited() and friends, but until someone
actually needs to use synchronize_srcu() during this window, this fix
is added churn for no benefit.

Finally, note that Tree SRCU's new srcu_init() function invokes
queue_work() rather than the queue_delayed_work() function that is
invoked post-boot.  The reason is that queue_delayed_work() will (as you
would expect) post a timer, and timers have not yet been initialized.
So use of queue_work() avoids the complaints about use of uninitialized
spinlocks that would otherwise result.  Besides, some delay is already
provide by the aforementioned fact that the queued work won't actually
be invoked until after the scheduler is up and running.

Requested-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
2018-08-30 16:10:19 -07:00
Mike Galbraith 894d45bbf7 rcu: Convert rcu_state.ofl_lock to raw_spinlock_t
1e64b15a4b ("rcu: Fix grace-period hangs due to race with CPU offline")
added spinlock_t ofl_lock to the rcu_state structure, then takes it with
preemption disabled during CPU offline, which gives the -rt patchset's
sleeping spinlock heartburn.

This commit therefore converts ->ofl_lock to raw_spinlock_t.

Signed-off-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
2018-08-30 16:03:54 -07:00
Paul E. McKenney 8d8a9d0e7e rcu: Remove obsolete ->dynticks_fqs and ->cond_resched_completed
The rcu_data structure's ->dynticks_fqs is incremented but never
accesses.  Its ->cond_resched_completed field isn't used at all.
This commit therefore removes both fields.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:03:53 -07:00
Paul E. McKenney dc5a4f2932 rcu: Switch ->dynticks to rcu_data structure, remove rcu_dynticks
This commit move ->dynticks from the rcu_dynticks structure to the
rcu_data structure, replacing the field of the same name.  It also updates
the code to access ->dynticks from the rcu_data structure and to use the
rcu_data structure rather than following to now-gone ->dynticks field
to the now-gone rcu_dynticks structure.  While in the area, this commit
also fixes up comments.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:03:52 -07:00
Paul E. McKenney 4c5273bf2b rcu: Switch dyntick nesting counters to rcu_data structure
This commit removes ->dynticks_nesting and ->dynticks_nmi_nesting from
the rcu_dynticks structure and updates the code to access them from the
rcu_data structure.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:03:51 -07:00
Paul E. McKenney 2dba13f0b6 rcu: Switch urgent quiescent-state requests to rcu_data structure
This commit removes ->rcu_need_heavy_qs and ->rcu_urgent_qs from the
rcu_dynticks structure and updates the code to access them from the
rcu_data structure.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:03:50 -07:00
Paul E. McKenney c458a89e96 rcu: Switch lazy counts to rcu_data structure
This commit removes ->all_lazy, ->nonlazy_posted and ->nonlazy_posted_snap
from the rcu_dynticks structure and updates the code to access them from
the rcu_data structure.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:03:49 -07:00
Paul E. McKenney 5998a75adb rcu: Switch last accelerate/advance to rcu_data structure
This commit removes ->last_accelerate and ->last_advance_all from the
rcu_dynticks structure and updates the code to access them from the
rcu_data structure.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:03:48 -07:00
Paul E. McKenney 0fd79e7521 rcu: Switch ->tick_nohz_enabled_snap to rcu_data structure
This commit removes ->tick_nohz_enabled_snap from the rcu_dynticks
structure and updates the code to access it from the rcu_data
structure.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:03:47 -07:00
Paul E. McKenney cc72046cc3 rcu: Merge rcu_dynticks structure into rcu_data structure
Now that there is only ever one rcu_data structure per CPU, there is no
need for a separate rcu_dynticks structure.  This commit therefore adds
the rcu_dynticks fields into the rcu_data structure in preparation for
removing the rcu_dynticks structure entirely.  Note that the ->dynticks
field will be handled specially because there is a field by that name
in both structures.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:03:47 -07:00
Paul E. McKenney df63fa5bc1 rcu: Convert "1UL << x" to "BIT(x)"
This commit saves a few characters by converting "1UL << x" to "BIT(x)".

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:03:46 -07:00
Paul E. McKenney fced9c8cfe rcu: Avoid resched_cpu() when rescheduling the current CPU
The resched_cpu() interface is quite handy, but it does acquire the
specified CPU's runqueue lock, which does not come for free.  This
commit therefore substitutes the following when directing resched_cpu()
at the current CPU:

	set_tsk_need_resched(current);
	set_preempt_need_resched();

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
2018-08-30 16:03:45 -07:00
Paul E. McKenney d3052109c0 rcu: More aggressively enlist scheduler aid for nohz_full CPUs
Because nohz_full CPUs can leave the scheduler-clock interrupt disabled
even when in kernel mode, RCU cannot rely on rcu_check_callbacks() to
enlist the scheduler's aid in extracting a quiescent state from such CPUs.
This commit therefore more aggressively uses resched_cpu() on nohz_full
CPUs that fail to pass through a quiescent state in a timely manner.
By default, the resched_cpu() beating starts 300 milliseconds into the
quiescent state.

While in the neighborhood, add a ->last_fqs_resched field to the rcu_data
structure in order to rate-limit resched_cpu() calls from the RCU
grace-period kthread.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:03:44 -07:00
Paul E. McKenney c06aed0e31 rcu: Compute jiffies_till_sched_qs from other kernel parameters
The jiffies_till_sched_qs value used to determine how old a grace period
must be before RCU enlists the help of the scheduler to force a quiescent
state on the holdout CPU.  Currently, this defaults to HZ/10 regardless of
system size and may be set only at boot time.  This can be a problem for
very large systems, because if the values of the jiffies_till_first_fqs
and jiffies_till_next_fqs kernel parameters are left at their defaults,
they are calculated to increase as the number of CPUs actually configured
on the system increases.  Thus, on a sufficiently large system, RCU would
enlist the help of the scheduler before the grace-period kthread had a
chance to scan for idle CPUs, which wastes CPU time.

This commit therefore allows jiffies_till_sched_qs to be set, if desired,
but if left as default, computes is as jiffies_till_first_fqs plus twice
jiffies_till_next_fqs, thus allowing three force-quiescent-state scans
for idle CPUs.  This scales with the number of CPUs, providing sensible
default values.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:03:43 -07:00
Paul E. McKenney 74de6960c9 rcu: Provide functions for determining if call_rcu() has been invoked
This commit adds rcu_head_init() and rcu_head_after_call_rcu() functions
to help RCU users detect when another CPU has passed the specified
rcu_head structure and function to call_rcu().  The rcu_head_init()
should be invoked before making the structure visible to RCU readers,
and then the rcu_head_after_call_rcu() may be invoked from within
an RCU read-side critical section on an rcu_head structure that
was obtained during a traversal of the data structure in question.
The rcu_head_after_call_rcu() function will return true if the rcu_head
structure has already been passed (with the specified function) to
call_rcu(), otherwise it will return false.

If rcu_head_init() has not been invoked on the rcu_head structure
or if the rcu_head (AKA callback) has already been invoked, then
rcu_head_after_call_rcu() will do WARN_ON_ONCE().

Reported-by: NeilBrown <neilb@suse.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
[ paulmck: Apply neilb naming feedback. ]
2018-08-30 16:03:42 -07:00
Paul E. McKenney 7e28c5af4e rcu: Eliminate ->rcu_qs_ctr from the rcu_dynticks structure
The ->rcu_qs_ctr counter was intended to allow providing a lightweight
report of a quiescent state to all RCU flavors.  But now that there is
only one flavor of RCU in any one running kernel, there is no point in
having this feature.  This commit therefore removes the ->rcu_qs_ctr
field from the rcu_dynticks structure and the ->rcu_qs_ctr_snap field
from the rcu_data structure.  This results in the "rqc" option to the
rcu_fqs trace event no longer being used, so this commit also removes the
"rqc" description from the header comment.

While in the neighborhood, this commit also causes the forward-progress
request .rcu_need_heavy_qs be set one jiffies_till_sched_qs interval
later in the grace period than the first setting of .rcu_urgent_qs.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:03:42 -07:00
Paul E. McKenney c5bacd9417 rcu: Motivate Tiny RCU forward progress
If a long-running CPU-bound in-kernel task invokes call_rcu(), the
callback won't be invoked until the next context switch.  If there are
no other runnable tasks (which is not an uncommon situation on deep
embedded systems), the callback might never be invoked.

This commit therefore causes rcu_check_callbacks() to ask the scheduler
for a context switch if there are callbacks posted that are still waiting
for a grace period.

Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:03:41 -07:00
Paul E. McKenney c116dba68d rcutorture: Dump reader protection sequence if failures or close calls
Now that RCU can have readers with multiple segments, it is quite
possible that a specific sequence of reader segments might result in
an rcutorture failure (reader spans a full grace period as detected
by one of the grace-period primitives) or an rcutorture close call
(reader potentially spans a full grace period based on reading out
the RCU implementation's grace-period counter, but with no ordering).
In such cases, it would clearly ease debugging if the offending specific
sequence was known.  For the first reader encountering a failure or a
close call, this commit therefore dumps out the segments, delay durations,
and whether or not the reader was preempted.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
[ paulmck: Mark variables static, as suggested by kbuild test robot. ]
2018-08-30 16:03:40 -07:00
Paul E. McKenney a0ef9ec241 rcu: Provide improved interrupt-from-idle check in rcu_check_callbacks()
The patch making need_resched() respond to urgent RCU-QS needs used
is_idle_task(current) to detect an interrupt from idle, which does work
reasonably, but is (in theory at least) vulnerable to loops containing
need_resched() invoked from within RCU_NONIDLE() or its tracepoint
equivalent.  This commit therefore moves rcu_is_cpu_rrupt_from_idle()
to a place from which rcu_check_callbacks() can invoke it and replaces
the is_idle_task(current) with rcu_is_cpu_rrupt_from_idle().

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:03:39 -07:00
Paul E. McKenney 92aa39e9dc rcu: Make need_resched() respond to urgent RCU-QS needs
The per-CPU rcu_dynticks.rcu_urgent_qs variable communicates an urgent
need for an RCU quiescent state from the force-quiescent-state processing
within the grace-period kthread to context switches and to cond_resched().
Unfortunately, such urgent needs are not communicated to need_resched(),
which is sometimes used to decide when to invoke cond_resched(), for
but one example, within the KVM vcpu_run() function.  As of v4.15, this
can result in synchronize_sched() being delayed by up to ten seconds,
which can be problematic, to say nothing of annoying.

This commit therefore checks rcu_dynticks.rcu_urgent_qs from within
rcu_check_callbacks(), which is invoked from the scheduling-clock
interrupt handler.  If the current task is not an idle task and is
not executing in usermode, a context switch is forced, and either way,
the rcu_dynticks.rcu_urgent_qs variable is set to false.  If the current
task is an idle task, then RCU's dyntick-idle code will detect the
quiescent state, so no further action is required.  Similarly, if the
task is executing in usermode, other code in rcu_check_callbacks() and
its called functions will report the corresponding quiescent state.

Reported-by: Marius Hillenbrand <mhillenb@amazon.de>
Reported-by: David Woodhouse <dwmw2@infradead.org>
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:03:39 -07:00
Paul E. McKenney dd46a7882c rcu: Inline _rcu_barrier() into its sole remaining caller
Because rcu_barrier() is a one-line wrapper function for _rcu_barrier()
and because nothing else calls _rcu_barrier(), this commit inlines
_rcu_barrier() into rcu_barrier().

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:03:39 -07:00
Paul E. McKenney 395a2f097e rcu: Define rcu_all_qs() only in !PREEMPT builds
Now that rcu_all_qs() is used only in !PREEMPT builds, move it to
tree_plugin.h so that it is defined only in those builds.  This in
turn means that rcu_momentary_dyntick_idle() is only used in !PREEMPT
builds, but it is simply marked __maybe_unused in order to keep it
near the rest of the dyntick-idle code.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:03:37 -07:00
Paul E. McKenney 06462efc80 rcu: Clean up flavor-related definitions and comments in update.c
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:03:36 -07:00
Paul E. McKenney 0ae86a2726 rcu: Clean up flavor-related definitions and comments in tree_plugin.h
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:03:35 -07:00
Paul E. McKenney 8fa946d428 rcu: Clean up flavor-related definitions and comments in tree_exp.h
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:03:35 -07:00
Paul E. McKenney 49918a54e6 rcu: Clean up flavor-related definitions and comments in tree.c
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:03:34 -07:00
Paul E. McKenney 679d3f3092 rcu: Clean up flavor-related definitions and comments in tiny.c
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:03:34 -07:00
Paul E. McKenney 6eb95cc450 rcu: Clean up flavor-related definitions and comments in srcutree.h
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:03:34 -07:00
Paul E. McKenney 62a1a94536 rcu: Clean up flavor-related definitions and comments in rcutorture.c
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:03:33 -07:00
Paul E. McKenney 7f87c036fe rcu: Clean up flavor-related definitions and comments in rcu.h
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:03:33 -07:00
Paul E. McKenney 8c1cf2da6f rcu: Clean up flavor-related definitions and comments in Kconfig
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:03:32 -07:00
Paul E. McKenney de3875d302 rcu: Remove now-unused rcutorture APIs
This commit removes rcu_sched_get_gp_seq(), rcu_bh_get_gp_seq(),
rcu_exp_batches_completed_sched(), rcu_sched_force_quiescent_state(),
and rcu_bh_force_quiescent_state(), which are no longer used because
rcutorture no longer does "rcu_bh" and "rcu_sched" torture types.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:03:30 -07:00
Paul E. McKenney 620d246065 rcuperf: Remove the "rcu_bh" and "sched" torture types
Now that the RCU-bh and RCU-sched update-side functions are simple
wrappers around their RCU counterparts, there isn't a whole lot of point
in testing them.  This commit therefore removes the "rcu_bh" and "sched"
torture types from rcuperf.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:03:30 -07:00
Paul E. McKenney c770c82a23 rcutorture: Remove the "rcu_bh" and "sched" torture types
Now that the RCU-bh and RCU-sched update-side functions are simple
wrappers around their RCU counterparts, there isn't a whole lot of point
in testing them.  This commit therefore removes the "rcu_bh" and "sched"
torture types from rcutorture.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:03:29 -07:00
Paul E. McKenney 72ce30dd1f rcu: Stop testing RCU-bh and RCU-sched
Now that the RCU-bh and RCU-sched update-side functions are simple
wrappers around their RCU counterparts, there isn't a whole lot of
point in testing them.  This commit therefore removes the self-test
capability and removes the corresponding kernel-boot parameters.
It also updates the various rcutorture .boot files to remove the
kernel boot parameters that call for testing RCU-bh and RCU-sched.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:03:29 -07:00
Paul E. McKenney 2ceebc0350 rcutorture: Add RCU-bh and RCU-sched support for extended readers
Since there is now a single consolidated RCU flavor, rcutorture
needs to test extending of RCU readers via rcu_read_lock_bh() and
rcu_read_lock_sched().  This commit adds this support, with added checks
(just like for local_bh_enable()) to ensure that rcu_read_unlock_bh()
will not be invoked while interrupts are disabled.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:03:27 -07:00
Paul E. McKenney a8bb74acd8 rcu: Consolidate RCU-sched update-side function definitions
This commit saves a few lines by consolidating the RCU-sched function
definitions at the end of include/linux/rcupdate.h.  This consolidation
also makes it easier to remove them all when the time comes.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:03:26 -07:00
Paul E. McKenney 4c7e9c1434 rcu: Consolidate RCU-bh update-side function definitions
This commit saves a few lines by consolidating the RCU-bh function
definitions at the end of include/linux/rcupdate.h.  This consolidation
also makes it easier to remove them all when the time comes.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:03:25 -07:00
Paul E. McKenney c3854a055b rcu: Pull rcu_gp_kthread() FQS loop into separate function
The rcu_gp_kthread() function is long and deeply indented, so this
commit pulls the loop that repeatedly invokes rcu_gp_fqs() into a new
rcu_gp_fqs_loop() function.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:03:24 -07:00
Paul E. McKenney 4e95020cdd rcu: Inline increment_cpu_stall_ticks() into its sole caller
Consolidation of the RCU flavors into one makes increment_cpu_stall_ticks()
a trivial one-line function with only one caller.  This commit therefore
inlines it.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:03:23 -07:00
Paul E. McKenney 8ff0b90780 rcu: Fix typo in force_qs_rnp()'s parameter's parameter
Pointers to rcu_data structures should be named rdp, not rsp.  This
commit therefore makes this change.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:03:23 -07:00
Paul E. McKenney eb7a665388 rcu: Eliminate initialization-time use of rsp
Now that there is only one rcu_state structure, there is less point in
maintaining a pointer to it.  This commit therefore replaces rsp with
&rcu_state in rcu_cpu_starting() and rcu_init_one().

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:03:22 -07:00
Paul E. McKenney ec9f5835f7 rcu: Eliminate RCU-barrier use of rsp
Now that there is only one rcu_state structure, there is less point
in maintaining a pointer to it.  This commit therefore replaces rsp
with &rcu_state in rcu_barrier_callback(), rcu_barrier_func(), and
_rcu_barrier().

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:03:22 -07:00
Paul E. McKenney 67a0edbf3c rcu: Eliminate quiescent-state and grace-period-nonstart use of rsp
Now that there is only one rcu_state structure, there is less point in
maintaining a pointer to it.  This commit therefore replaces rsp with
&rcu_state in rcu_report_qs_rnp(), force_quiescent_state(), and
rcu_check_gp_start_stall().

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:03:21 -07:00
Paul E. McKenney 3c779dfef2 rcu: Eliminate callback-invocation/invocation use of rsp
Now that there is only one rcu_state structure, there is less point in
maintaining a pointer to it.  This commit therefore replaces rsp with
&rcu_state in rcu_do_batch(), invoke_rcu_callbacks(), and __call_rcu().

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:03:21 -07:00
Paul E. McKenney 9cbc5b9702 rcu: Eliminate grace-period management code use of rsp
Now that there is only one rcu_state structure, there is less point
in maintaining a pointer to it.  This commit therefore replaces
rsp with &rcu_state in rcu_start_this_gp(), rcu_accelerate_cbs(),
__note_gp_changes(), rcu_gp_init(), rcu_gp_fqs(), rcu_gp_cleanup(),
rcu_gp_kthread(), and rcu_report_qs_rsp().

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:03:20 -07:00
Paul E. McKenney 4c6ed43708 rcu: Eliminate stall-warning use of rsp
Now that there is only one rcu_state structure, there is less point
in maintaining a pointer to it.  This commit therefore replaces rsp
with &rcu_state in print_other_cpu_stall(), print_cpu_stall(), and
check_cpu_stall().

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:03:20 -07:00
Paul E. McKenney 7cba4775ba rcu: Restructure rcu_check_gp_kthread_starvation()
This commit removes the rsp and gpa local variables, repurposes the j
local variable and adds a gpk (GP kthread) local to improve readability.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:03:19 -07:00
Paul E. McKenney f7dd7d44fd rcu: Simplify rcutorture_get_gp_data()
This commit restructures rcutorture_get_gp_data() to take advantage of
the fact that there is only one flavor of RCU.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:03:19 -07:00
Paul E. McKenney b97d23c51c rcu: Remove for_each_rcu_flavor() flavor-traversal macro
Now that there is only ever a single flavor of RCU in a given kernel
build, there isn't a whole lot of point in having a flavor-traversal
macro.  This commit therefore removes it and converts calls to it to
straightline code, inlining trivial functions as appropriate.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:03:18 -07:00
Paul E. McKenney 564a9ae604 rcu: Remove last non-flavor-traversal rsp local variable from tree_plugin.h
This commit removes the last non-flavor-traversal rsp local variable from
kernel/rcu/tree_plugin.h in favor of &rcu_state.  The flavor-traversal
locals will be removed with the removal of flavor traversal.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:03:17 -07:00
Paul E. McKenney 88d1bead85 rcu: Remove rcu_data structure's ->rsp field
Now that there is only one rcu_state structure, there is no need for the
rcu_data structure to indicate which it corresponds to.  This commit
therefore removes the rcu_data structure's ->rsp field, replacing all
remaining uses of it with &rcu_state.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:03:17 -07:00
Paul E. McKenney aedf4ba984 rcu: Remove rsp parameter from rcu_node tree accessor macros
There now is only one rcu_state structure in a given build of the Linux
kernel, so there is no need to pass it as a parameter to RCU's rcu_node
tree's accessor macros.  This commit therefore removes the rsp parameter
from those macros in kernel/rcu/rcu.h, and removes some now-unused rsp
local variables while in the area.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:03:16 -07:00
Paul E. McKenney 63d4c8c979 rcu: Remove rsp parameter from expedited grace-period functions
There now is only one rcu_state structure in a given build of the
Linux kernel, so there is no need to pass it as a parameter to
RCU's functions.  This commit therefore removes the rsp parameter
from the code in kernel/rcu/tree_exp.h, and removes all of the
rsp local variables while in the area.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:03:14 -07:00
Paul E. McKenney 4580b0541b rcu: Remove rsp parameter from no-CBs CPU functions
There now is only one rcu_state structure in a given build of the
Linux kernel, so there is no need to pass it as a parameter to
RCU's functions.  This commit therefore removes the rsp parameter
from rcu_nocb_cpu_needs_barrier(), rcu_spawn_one_nocb_kthread(),
rcu_organize_nocb_kthreads(), rcu_nocb_cpu_needs_barrier(), and
rcu_nohz_full_cpu().

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:03:13 -07:00
Paul E. McKenney b21ebed951 rcu: Remove rsp parameter from print_cpu_stall_info()
There now is only one rcu_state structure in a given build of the
Linux kernel, so there is no need to pass it as a parameter to RCU's
functions.  This commit therefore removes the rsp parameter from
print_cpu_stall_info().

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:03:12 -07:00
Paul E. McKenney 6dbfdc1409 rcu: Remove rsp parameter from rcu_spawn_one_boost_kthread()
There now is only one rcu_state structure in a given build of the
Linux kernel, so there is no need to pass it as a parameter to RCU's
functions.  This commit therefore removes the rsp parameter from
rcu_spawn_one_boost_kthread().

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:03:11 -07:00
Paul E. McKenney 81ab59a3ad rcu: Remove rsp parameter from dump_blkd_tasks() and friend
There now is only one rcu_state structure in a given build of the
Linux kernel, so there is no need to pass it as a parameter to RCU's
functions.  This commit therefore removes the rsp parameter from
dump_blkd_tasks() and rcu_preempt_blocked_readers_cgp().

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:03:10 -07:00
Paul E. McKenney a2887cd85f rcu: Remove rsp parameter from rcu_print_detail_task_stall()
There now is only one rcu_state structure in a given build of the
Linux kernel, so there is no need to pass it as a parameter to RCU's
functions.  This commit therefore removes the rsp parameter from
rcu_print_detail_task_stall().

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:03:09 -07:00
Paul E. McKenney b8bb1f63cf rcu: Remove rsp parameter from rcu_init_one() and friends
There now is only one rcu_state structure in a given build of the
Linux kernel, so there is no need to pass it as a parameter to RCU's
functions.  This commit therefore removes the rsp parameter from
rcu_init_one() and rcu_dump_rcu_node_tree().

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:03:09 -07:00
Paul E. McKenney 53b46303da rcu: Remove rsp parameter from rcu_boot_init_percpu_data() and friends
There now is only one rcu_state structure in a given build of
the Linux kernel, so there is no need to pass it as a parameter
to RCU's functions.  This commit therefore removes the rsp
parameter from rcu_boot_init_percpu_data(), rcu_init_percpu_data(),
rcu_cleanup_dying_idle_cpu(), and rcu_migrate_callbacks().  While in
the neighborhood, line the last three into rcutree_prepare_cpu(),
rcu_report_dead() and rcutree_migrate_callbacks(), respectively.
This also gets rid of the for_each_rcu_flavor() calls that were in
those tree functions.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:03:08 -07:00
Paul E. McKenney 8344b871b1 rcu: Remove rsp parameter from _rcu_barrier() and friends
There now is only one rcu_state structure in a given build of the
Linux kernel, so there is no need to pass it as a parameter to RCU's
functions.  This commit therefore removes the rsp parameter from
_rcu_barrier_trace() and _rcu_barrier().

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:03:08 -07:00
Paul E. McKenney 98ece508b5 rcu: Remove rsp parameter from __rcu_pending()
There now is only one rcu_state structure in a given build of the Linux
kernel, so there is no need to pass it as a parameter to RCU's functions.
This commit therefore removes the rsp parameter from __rcu_pending(),
and also inlines it into rcu_pending(), removing the for_each_rcu_flavor()
while in the neighborhood..

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:03:07 -07:00
Paul E. McKenney 5c7d89676b rcu: Remove rsp parameter from __call_rcu() and friend
There now is only one rcu_state structure in a given build of the
Linux kernel, so there is no need to pass it as a parameter to RCU's
functions.  This commit therefore removes the rsp parameter from
__call_rcu_core() and __call_rcu().

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:03:07 -07:00
Paul E. McKenney b049fdf8e3 rcu: Remove rsp parameter from __rcu_process_callbacks()
There now is only one rcu_state structure in a given build of the
Linux kernel, so there is no need to pass it as a parameter to RCU's
functions.  This commit therefore removes the rsp parameter from
__rcu_process_callbacks(), and also inlines it into rcu_process_callbacks(),
removing the for_each_rcu_flavor() while in the neighborhood.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:03:06 -07:00
Paul E. McKenney b96f9dc4fb rcu: Remove rsp parameter from rcu_check_gp_start_stall()
There now is only one rcu_state structure in a given build of the
Linux kernel, so there is no need to pass it as a parameter to RCU's
functions.  This commit therefore removes the rsp parameter from
rcu_check_gp_start_stall().

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:03:06 -07:00
Paul E. McKenney e9ecb780fe rcu: Remove rsp parameter from force-quiescent-state functions
There now is only one rcu_state structure in a given build of the
Linux kernel, so there is no need to pass it as a parameter to RCU's
functions.  This commit therefore removes the rsp parameter from
force_qs_rnp() and force_quiescent_state().

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:03:05 -07:00
Paul E. McKenney 5bb5d09cc4 rcu: Remove rsp parameter from rcu_do_batch()
There now is only one rcu_state structure in a given build of the
Linux kernel, so there is no need to pass it as a parameter to RCU's
functions.  This commit therefore removes the rsp parameter from
rcu_do_batch().

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:03:05 -07:00
Paul E. McKenney 780cd59083 rcu: Remove rsp parameter from CPU hotplug functions
There now is only one rcu_state structure in a given build of the
Linux kernel, so there is no need to pass it as a parameter to RCU's
functions.  This commit therefore removes the rsp parameter from
rcu_cleanup_dying_cpu() and rcu_cleanup_dead_cpu().  And, as long as
we are in the neighborhood, inlines them into rcutree_dying_cpu() and
rcutree_dead_cpu(), respectively.  This also eliminates a pair of
for_each_rcu_flavor() loops.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:03:04 -07:00
Paul E. McKenney 8087d3e3c4 rcu: Remove rsp parameter from rcu_check_quiescent_state()
There now is only one rcu_state structure in a given build of the
Linux kernel, so there is no need to pass it as a parameter to RCU's
functions.  This commit therefore removes the rsp parameter from
rcu_check_quiescent_state().

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:03:04 -07:00
Paul E. McKenney 0854a05c9f rcu: Remove rsp parameter from rcu_gp_kthread() and friends
There now is only one rcu_state structure in a given build of the
Linux kernel, so there is no need to pass it as a parameter to RCU's
functions.  This commit therefore removes the rsp parameter from
rcu_gp_init(), rcu_gp_fqs_check_wake(), rcu_gp_fqs(), rcu_gp_cleanup(),
and rcu_gp_kthread().

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:03:03 -07:00
Paul E. McKenney 22212332c1 rcu: Remove rsp parameter from rcu_gp_slow()
There now is only one rcu_state structure in a given build of the
Linux kernel, so there is no need to pass it as a parameter to RCU's
functions.  This commit therefore removes the rsp parameter from
rcu_gp_slow().

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:03:03 -07:00
Paul E. McKenney 15cabdffbb rcu: Remove rsp parameter from note_gp_changes()
There now is only one rcu_state structure in a given build of the
Linux kernel, so there is no need to pass it as a parameter to RCU's
functions.  This commit therefore removes the rsp parameter from
note_gp_changes().

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:03:02 -07:00
Paul E. McKenney c7e48f7ba3 rcu: Remove rsp parameter from __note_gp_changes()
There now is only one rcu_state structure in a given build of the
Linux kernel, so there is no need to pass it as a parameter to RCU's
functions.  This commit therefore removes the rsp parameter from
__note_gp_changes().

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:03:01 -07:00
Paul E. McKenney 834f56bf54 rcu: Remove rsp parameter from rcu_advance_cbs()
There now is only one rcu_state structure in a given build of the
Linux kernel, so there is no need to pass it as a parameter to RCU's
functions.  This commit therefore removes the rsp parameter from
rcu_advance_cbs().

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:03:01 -07:00
Paul E. McKenney c6e09b97b9 rcu: Remove rsp parameter from rcu_accelerate_cbs_unlocked()
There now is only one rcu_state structure in a given build of the
Linux kernel, so there is no need to pass it as a parameter to RCU's
functions.  This commit therefore removes the rsp parameter from
rcu_accelerate_cbs_unlocked().

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:03:00 -07:00
Paul E. McKenney 02f501423d rcu: Remove rsp parameter from rcu_accelerate_cbs()
There now is only one rcu_state structure in a given build of the
Linux kernel, so there is no need to pass it as a parameter to RCU's
functions.  This commit therefore removes the rsp parameter from
rcu_accelerate_cbs().

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:03:00 -07:00
Paul E. McKenney 532c00c97f rcu: Remove rsp parameter from rcu_gp_kthread_wake()
There now is only one rcu_state structure in a given build of the
Linux kernel, so there is no need to pass it as a parameter to RCU's
functions.  This commit therefore removes the rsp parameter from
rcu_gp_kthread_wake().

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:02:59 -07:00
Paul E. McKenney 3481f2eab0 rcu: Remove rsp parameter from rcu_future_gp_cleanup()
There now is only one rcu_state structure in a given build of the
Linux kernel, so there is no need to pass it as a parameter to RCU's
functions.  This commit therefore removes the rsp parameter from
rcu_future_gp_cleanup().

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:02:59 -07:00
Paul E. McKenney ea12ff2b7d rcu: Remove rsp parameter from check_cpu_stall()
There now is only one rcu_state structure in a given build of the
Linux kernel, so there is no need to pass it as a parameter to RCU's
functions.  This commit therefore removes the rsp parameter from
check_cpu_stall().

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:02:58 -07:00
Paul E. McKenney 4e8b8e08f9 rcu: Remove rsp parameter from print_cpu_stall()
There now is only one rcu_state structure in a given build of the
Linux kernel, so there is no need to pass it as a parameter to RCU's
functions.  This commit therefore removes the rsp parameter from
print_cpu_stall().

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:02:58 -07:00
Paul E. McKenney a91e7e58b1 rcu: Remove rsp parameter from print_other_cpu_stall()
There now is only one rcu_state structure in a given build of the
Linux kernel, so there is no need to pass it as a parameter to RCU's
functions.  This commit therefore removes the rsp parameter from
print_other_cpu_stall().

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:02:57 -07:00
Paul E. McKenney e1741c69d4 rcu: Remove rsp parameter from rcu_stall_kick_kthreads()
There now is only one rcu_state structure in a given build of the
Linux kernel, so there is no need to pass it as a parameter to RCU's
functions.  This commit therefore removes the rsp parameter from
rcu_stall_kick_kthreads().

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:02:57 -07:00
Paul E. McKenney 33dbdbf025 rcu: Remove rsp parameter from rcu_dump_cpu_stacks()
There now is only one rcu_state structure in a given build of the
Linux kernel, so there is no need to pass it as a parameter to RCU's
functions.  This commit therefore removes the rsp parameter from
rcu_dump_cpu_stacks().

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:02:56 -07:00
Paul E. McKenney 8fd119b652 rcu: Remove rsp parameter from rcu_check_gp_kthread_starvation()
There now is only one rcu_state structure in a given build of the
Linux kernel, so there is no need to pass it as a parameter to RCU's
functions.  This commit therefore removes the rsp parameter from
rcu_check_gp_kthread_starvation().

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:02:56 -07:00
Paul E. McKenney ad3832e974 rcu: Remove rsp parameter from record_gp_stall_check_time()
There now is only one rcu_state structure in a given build of the
Linux kernel, so there is no need to pass it as a parameter to RCU's
functions.  This commit therefore removes the rsp parameter from
record_gp_stall_check_time().

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:02:55 -07:00
Paul E. McKenney 336a4f6c45 rcu: Remove rsp parameter from rcu_get_root()
There now is only one rcu_state structure in a given build of the
Linux kernel, so there is no need to pass it as a parameter to RCU's
functions.  This commit therefore removes the rsp parameter from
rcu_get_root().

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:02:55 -07:00
Paul E. McKenney de8e87305a rcu: Remove rsp parameter from rcu_gp_in_progress()
There now is only one rcu_state structure in a given build of the
Linux kernel, so there is no need to pass it as a parameter to RCU's
functions.  This commit therefore removes the rsp parameter from
rcu_gp_in_progress().

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:02:54 -07:00
Paul E. McKenney 33085c469a rcu: Remove rsp parameter from rcu_report_qs_rdp()
There now is only one rcu_state structure in a given build of the
Linux kernel, so there is no need to pass it as a parameter to RCU's
functions.  This commit therefore removes the rsp parameter from
rcu_report_qs_rdp().

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:02:53 -07:00
Paul E. McKenney 139ad4da5a rcu: Remove rsp parameter from rcu_report_unblock_qs_rnp()
There now is only one rcu_state structure in a given build of the
Linux kernel, so there is no need to pass it as a parameter to RCU's
functions.  This commit therefore removes the rsp parameter from
rcu_report_unblock_qs_rnp(), which is particularly appropriate in
this case given that this parameter is no longer used.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:02:53 -07:00
Paul E. McKenney aff4e9ede5 rcu: Remove rsp parameter from rcu_report_qs_rsp()
There now is only one rcu_state structure in a given build of the
Linux kernel, so there is no need to pass it as a parameter to RCU's
functions.  This commit therefore removes the rsp parameter from
rcu_report_qs_rsp().

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:02:52 -07:00
Paul E. McKenney b50912d0b5 rcu: Remove rsp parameter from rcu_report_qs_rnp()
There now is only one rcu_state structure in a given build of the
Linux kernel, so there is no need to pass it as a parameter to RCU's
functions.  This commit therefore removes the rsp parameter from
rcu_report_qs_rnp().

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:02:51 -07:00
Paul E. McKenney 2280ee5a7d rcu: Remove rcu_data_p pointer to default rcu_data structure
The rcu_data_p pointer references the default set of per-CPU rcu_data
structures, that is, those that call_rcu() uses, as opposed to
call_rcu_bh() and sometimes call_rcu_sched().  But there is now only one
set of per-CPU rcu_data structures, so that one set is by definition
the default, which means that the rcu_data_p pointer no longer serves
any useful purpose.  This commit therefore removes it.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:02:51 -07:00
Paul E. McKenney 16fc9c600b rcu: Remove rcu_state_p pointer to default rcu_state structure
The rcu_state_p pointer references the default rcu_state structure,
that is, the one that call_rcu() uses, as opposed to call_rcu_bh()
and sometimes call_rcu_sched().  But there is now only one rcu_state
structure, so that one structure is by definition the default, which
means that the rcu_state_p pointer no longer serves any useful purpose.
This commit therefore removes it.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:02:50 -07:00
Paul E. McKenney da1df50d16 rcu: Remove rcu_state structure's ->rda field
The rcu_state structure's ->rda field was used to find the per-CPU
rcu_data structures corresponding to that rcu_state structure.  But now
there is only one rcu_state structure (creatively named "rcu_state")
and one set of per-CPU rcu_data structures (creatively named "rcu_data").
Therefore, uses of the ->rda field can always be replaced by "rcu_data,
and this commit makes that change and removes the ->rda field.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:02:49 -07:00
Paul E. McKenney ec5dd444b6 rcu: Eliminate rcu_state structure's ->call field
The rcu_state structure's ->call field references the corresponding RCU
flavor's call_rcu() function.  However, now that there is only ever one
rcu_state structure in a given build of the Linux kernel, and that flavor
uses plain old call_rcu(), there is not a lot of point in continuing to
have the ->call field.  This commit therefore removes it.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:02:48 -07:00
Paul E. McKenney 358be2d368 rcu: Remove RCU_STATE_INITIALIZER()
Now that a given build of the Linux kernel has only one set of rcu_state,
rcu_node, and rcu_data structures, there is no point in creating a macro
to declare and compile-time initialize them.  This commit therefore
just does normal declaration and compile-time initialization of these
structures.  While in the area, this commit also removes #ifndefs of
the no-longer-ever-defined preprocessor macro RCU_TREE_NONCORE.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:02:47 -07:00
Paul E. McKenney 709fdce754 rcu: Express Tiny RCU updates in terms of RCU rather than RCU-sched
This commit renames Tiny RCU functions so that the lowest level of
functionality is RCU (e.g., synchronize_rcu()) rather than RCU-sched
(e.g., synchronize_sched()).  This provides greater naming compatibility
with Tree RCU, which will in turn permit more LoC removal once
the RCU-sched and RCU-bh update-side API is removed.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
[ paulmck: Fix Tiny call_rcu()'s EXPORT_SYMBOL() in response to a bug
  report from kbuild test robot. ]
2018-08-30 16:02:46 -07:00
Paul E. McKenney 45975c7d21 rcu: Define RCU-sched API in terms of RCU for Tree RCU PREEMPT builds
Now that RCU-preempt knows about preemption disabling, its implementation
of synchronize_rcu() works for synchronize_sched(), and likewise for the
other RCU-sched update-side API members.  This commit therefore confines
the RCU-sched update-side code to CONFIG_PREEMPT=n builds, and defines
RCU-sched's update-side API members in terms of those of RCU-preempt.

This means that any given build of the Linux kernel has only one
update-side flavor of RCU, namely RCU-preempt for CONFIG_PREEMPT=y builds
and RCU-sched for CONFIG_PREEMPT=n builds.  This in turn means that kernels
built with CONFIG_RCU_NOCB_CPU=y have only one rcuo kthread per CPU.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Andi Kleen <ak@linux.intel.com>
2018-08-30 16:02:45 -07:00
Paul E. McKenney 4cf439a200 rcu: Fix typo in rcu_get_gp_kthreads_prio() header comment
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:02:43 -07:00
Paul E. McKenney 2bbfc25b09 rcu: Drop "wake" parameter from rcu_report_exp_rdp()
The rcu_report_exp_rdp() function is always invoked with its "wake"
argument set to "true", so this commit drops this parameter.  The only
potential call site that would use "false" is in the code driving the
expedited grace period, and that code uses rcu_report_exp_cpu_mult()
instead, which therefore retains its "wake" parameter.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:02:43 -07:00
Paul E. McKenney 82fcecfa81 rcu: Update comments and help text for no more RCU-bh updaters
This commit updates comments and help text to account for the fact that
RCU-bh update-side functions are now simple wrappers for their RCU or
RCU-sched counterparts.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:02:42 -07:00
Paul E. McKenney 65cfe3583b rcu: Define RCU-bh update API in terms of RCU
Now that the main RCU API knows about softirq disabling and softirq's
quiescent states, the RCU-bh update code can be dispensed with.
This commit therefore removes the RCU-bh update-side implementation and
defines RCU-bh's update-side API in terms of that of either RCU-preempt or
RCU-sched, depending on the setting of the CONFIG_PREEMPT Kconfig option.

In kernels built with CONFIG_RCU_NOCB_CPU=y this has the knock-on effect
of reducing by one the number of rcuo kthreads per CPU.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:02:40 -07:00
Paul E. McKenney ba1c64c272 rcu: Report expedited grace periods at context-switch time
This commit reduces the latency of expedited RCU grace periods by
reporting a quiescent state for the CPU at context-switch time.
In CONFIG_PREEMPT=y kernels, if the outgoing task is still within an
RCU read-side critical section (and thus still blocking some grace
period, perhaps including this expedited grace period), then that task
will already have been placed on one of the leaf rcu_node structures'
->blkd_tasks list.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30 16:02:38 -07:00