Ming reported soft lockups occurring when running xfstest due to
the following tip:locking/core commit:
b3fd4f03ca ("locking/rwsem: Avoid deceiving lock spinners")
When doing optimistic spinning in rwsem, threads should stop
spinning when the lock owner is not running. While a thread is
spinning on owner, if the owner reschedules, owner->on_cpu
returns false and we stop spinning.
However, this commit essentially caused the check to get
ignored because when we break out of the spin loop due to
!on_cpu, we continue spinning if sem->owner != NULL.
This patch fixes this by making sure we stop spinning if the
owner is not running. Furthermore, just like with mutexes,
refactor the code such that we don't have separate checks for
owner_running(). This makes it more straightforward in terms of
why we exit the spin on owner loop and we would also avoid
needing to "guess" why we broke out of the loop to make this
more readable.
Reported-and-tested-by: Ming Lei <ming.lei@canonical.com>
Signed-off-by: Jason Low <jason.low2@hp.com>
Acked-by: Davidlohr Bueso <dave@stgolabs.net>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Dave Jones <davej@codemonkey.org.uk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Michel Lespinasse <walken@google.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sasha Levin <sasha.levin@oracle.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Link: http://lkml.kernel.org/r/1425714331.2475.388.camel@j-VirtualBox
Signed-off-by: Ingo Molnar <mingo@kernel.org>
With the new standardized functions, we can replace all
ACCESS_ONCE() calls across relevant locking - this includes
lockref and seqlock while at it.
ACCESS_ONCE() does not work reliably on non-scalar types.
For example gcc 4.6 and 4.7 might remove the volatile tag
for such accesses during the SRA (scalar replacement of
aggregates) step:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58145
Update the new calls regardless of if it is a scalar type,
this is cleaner than having three alternatives.
Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/1424662301.6539.18.camel@stgolabs.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'v4.0-rc1' into locking/core, to refresh the tree before merging new changes
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Pull MIPS updates from Ralf Baechle:
"This is the main pull request for MIPS:
- a number of fixes that didn't make the 3.19 release.
- a number of cleanups.
- preliminary support for Cavium's Octeon 3 SOCs which feature up to
48 MIPS64 R3 cores with FPU and hardware virtualization.
- support for MIPS R6 processors.
Revision 6 of the MIPS architecture is a major revision of the MIPS
architecture which does away with many of original sins of the
architecture such as branch delay slots. This and other changes in
R6 require major changes throughout the entire MIPS core
architecture code and make up for the lion share of this pull
request.
- finally some preparatory work for eXtendend Physical Address
support, which allows support of up to 40 bit of physical address
space on 32 bit processors"
[ Ahh, MIPS can't leave the PAE brain damage alone. It's like
every CPU architect has to make that mistake, but pee in the snow
by changing the TLA. But whether it's called PAE, LPAE or XPA,
it's horrid crud - Linus ]
* 'upstream' of git://git.linux-mips.org/pub/scm/ralf/upstream-linus: (114 commits)
MIPS: sead3: Corrected get_c0_perfcount_int
MIPS: mm: Remove dead macro definitions
MIPS: OCTEON: irq: add CIB and other fixes
MIPS: OCTEON: Don't do acknowledge operations for level triggered irqs.
MIPS: OCTEON: More OCTEONIII support
MIPS: OCTEON: Remove setting of processor specific CVMCTL icache bits.
MIPS: OCTEON: Core-15169 Workaround and general CVMSEG cleanup.
MIPS: OCTEON: Update octeon-model.h code for new SoCs.
MIPS: OCTEON: Implement DCache errata workaround for all CN6XXX
MIPS: OCTEON: Add little-endian support to asm/octeon/octeon.h
MIPS: OCTEON: Implement the core-16057 workaround
MIPS: OCTEON: Delete unused COP2 saving code
MIPS: OCTEON: Use correct instruction to read 64-bit COP0 register
MIPS: OCTEON: Save and restore CP2 SHA3 state
MIPS: OCTEON: Fix FP context save.
MIPS: OCTEON: Save/Restore wider multiply registers in OCTEON III CPUs
MIPS: boot: Provide more uImage options
MIPS: Remove unneeded #ifdef __KERNEL__ from asm/processor.h
MIPS: ip22-gio: Remove legacy suspend/resume support
mips: pci: Add ifdef around pci_proc_domain
...
Pull ntp fix from Ingo Molnar:
"An adjtimex interface regression fix for 32-bit systems"
[ A check that was added in a previous commit is really only a concern
for 64bit systems, but was applied to both 32 and 64bit systems, which
results in breaking 32bit systems.
Thus the fix here is to make the check only apply to 64bit systems ]
* 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
ntp: Fixup adjtimex freq validation on 32-bit systems
Pull locking fixes from Ingo Molnar:
"Two fixes: the paravirt spin_unlock() corruption/crash fix, and an
rtmutex NULL dereference crash fix"
* 'locking-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/spinlocks/paravirt: Fix memory corruption on unlock
locking/rtmutex: Avoid a NULL pointer dereference on deadlock
Pull scheduler fixes from Ingo Molnar:
"Thiscontains misc fixes: preempt_schedule_common() and io_schedule()
recursion fixes, sched/dl fixes, a completion_done() revert, two
sched/rt fixes and a comment update patch"
* 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
sched/rt: Avoid obvious configuration fail
sched/autogroup: Fix failure to set cpu.rt_runtime_us
sched/dl: Do update_rq_clock() in yield_task_dl()
sched: Prevent recursion in io_schedule()
sched/completion: Serialize completion_done() with complete()
sched: Fix preempt_schedule_common() triggering tracing recursion
sched/dl: Prevent enqueue of a sleeping task in dl_task_timer()
sched: Make dl_task_time() use task_rq_lock()
sched: Clarify ordering between task_rq_lock() and move_queued_task()
Pull rcu fix and x86 irq fix from Ingo Molnar:
- Fix a bug that caused an RCU warning splat.
- Two x86 irq related fixes: a hotplug crash fix and an ACPI IRQ
registry fix.
* 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
rcu: Clear need_qs flag to prevent splat
* 'irq-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/irq: Check for valid irq descriptor in check_irq_vectors_for_cpu_disable()
x86/irq: Fix regression caused by commit b568b8601f
* KDB: improved searching
* No longer enter debug core on panic if panic timeout is set
KGDB/KDB regressions / cleanups
* fix pdf doc build errors
* prevent junk characters on kdb console from printk levels
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Merge tag 'for_linux-3.20-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/jwessel/kgdb
Pull kgdb/kdb updates from Jason Wessel:
"KGDB/KDB New:
- KDB: improved searching
- No longer enter debug core on panic if panic timeout is set
KGDB/KDB regressions / cleanups
- fix pdf doc build errors
- prevent junk characters on kdb console from printk levels"
* tag 'for_linux-3.20-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/jwessel/kgdb:
kgdb, docs: Fix <para> pdfdocs build errors
debug: prevent entering debug mode on panic/exception.
kdb: Const qualifier for kdb_getstr's prompt argument
kdb: Provide forward search at more prompt
kdb: Fix a prompt management bug when using | grep
kdb: Remove stack dump when entering kgdb due to NMI
kdb: Avoid printing KERN_ levels to consoles
kdb: Fix off by one error in kdb_cpu()
kdb: fix incorrect counts in KDB summary command output
On non-developer devices, kgdb prevents the device from rebooting
after a panic.
Incase of panics and exceptions, to allow the device to reboot, prevent
entering debug mode to avoid getting stuck waiting for the user to
interact with debugger.
To avoid entering the debugger on panic/exception without any extra
configuration, panic_timeout is being used which can be set via
/proc/sys/kernel/panic at run time and CONFIG_PANIC_TIMEOUT sets the
default value.
Setting panic_timeout indicates that the user requested machine to
perform unattended reboot after panic. We dont want to get stuck waiting
for the user input incase of panic.
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: kgdb-bugreport@lists.sourceforge.net
Cc: linux-kernel@vger.kernel.org
Cc: Android Kernel Team <kernel-team@android.com>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Sumit Semwal <sumit.semwal@linaro.org>
Signed-off-by: Colin Cross <ccross@android.com>
[Kiran: Added context to commit message.
panic_timeout is used instead of break_on_panic and
break_on_exception to honor CONFIG_PANIC_TIMEOUT
Modified the commit as per community feedback]
Signed-off-by: Kiran Raparthy <kiran.kumar@linaro.org>
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
All current callers of kdb_getstr() can pass constant pointers via the
prompt argument. This patch adds a const qualification to make explicit
the fact that this is safe.
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
Currently kdb allows the output of comamnds to be filtered using the
| grep feature. This is useful but does not permit the output emitted
shortly after a string match to be examined without wading through the
entire unfiltered output of the command. Such a feature is particularly
useful to navigate function traces because these traces often have a
useful trigger string *before* the point of interest.
This patch reuses the existing filtering logic to introduce a simple
forward search to kdb that can be triggered from the more prompt.
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
Currently when the "| grep" feature is used to filter the output of a
command then the prompt is not displayed for the subsequent command.
Likewise any characters typed by the user are also not echoed to the
display. This rather disconcerting problem eventually corrects itself
when the user presses Enter and the kdb_grepping_flag is cleared as
kdb_parse() tries to make sense of whatever they typed.
This patch resolves the problem by moving the clearing of this flag
from the middle of command processing to the beginning.
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
Issuing a stack dump feels ergonomically wrong when entering due to NMI.
Entering due to NMI is normally a reaction to a user request, either the
NMI button on a server or a "magic knock" on a UART. Therefore the
backtrace behaviour on entry due to NMI should be like SysRq-g (no stack
dump) rather than like oops.
Note also that the stack dump does not offer any information that
cannot be trivial retrieved using the 'bt' command.
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
Currently when kdb traps printk messages then the raw log level prefix
(consisting of '\001' followed by a numeral) does not get stripped off
before the message is issued to the various I/O handlers supported by
kdb. This causes annoying visual noise as well as causing problems
grepping for ^. It is also a change of behaviour compared to normal usage
of printk() usage. For example <SysRq>-h ends up with different output to
that of kdb's "sr h".
This patch addresses the problem by stripping log levels from messages
before they are issued to the I/O handlers. printk() which can also
act as an i/o handler in some cases is special cased; if the caller
provided a log level then the prefix will be preserved when sent to
printk().
The addition of non-printable characters to the output of kdb commands is a
regression, albeit and extremely elderly one, introduced by commit
04d2c8c83d ("printk: convert the format for KERN_<LEVEL> to a 2 byte
pattern"). Note also that this patch does *not* restore the original
behaviour from v3.5. Instead it makes printk() from within a kdb command
display the message without any prefix (i.e. like printk() normally does).
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Cc: Joe Perches <joe@perches.com>
Cc: stable@vger.kernel.org
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
There was a follow on replacement patch against the prior
"kgdb: Timeout if secondary CPUs ignore the roundup".
See: https://lkml.org/lkml/2015/1/7/442
This patch is the delta vs the patch that was committed upstream:
* Fix an off-by-one error in kdb_cpu().
* Replace NR_CPUS with CONFIG_NR_CPUS to tell checkpatch that we
really want a static limit.
* Removed the "KGDB: " prefix from the pr_crit() in debug_core.c
(kgdb-next contains a patch which introduced pr_fmt() to this file
to the tag will now be applied automatically).
Cc: Daniel Thompson <daniel.thompson@linaro.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
The output of KDB 'summary' command should report MemTotal, MemFree
and Buffers output in kB. Current codes report in unit of pages.
A define of K(x) as
is defined in the code, but not used.
This patch would apply the define to convert the values to kB.
Please include me on Cc on replies. I do not subscribe to linux-kernel.
Signed-off-by: Jay Lan <jlan@sgi.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
Pull kbuild updates from Michal Marek:
- several cleanups in kbuild
- serialize multiple *config targets so that 'make defconfig kvmconfig'
works
- The cc-ifversion macro got support for an else-branch
* 'kbuild' of git://git.kernel.org/pub/scm/linux/kernel/git/mmarek/kbuild:
kbuild,gcov: simplify kernel/gcov/Makefile more
kbuild: allow cc-ifversion to have the argument for false condition
kbuild,gcov: simplify kernel/gcov/Makefile
kbuild,gcov: remove unnecessary workaround
kbuild: do not add $(call ...) to invoke cc-version or cc-fullversion
kbuild: fix cc-ifversion macro
kbuild: drop $(version_h) from MRPROPER_FILES
kbuild: use mixed-targets when two or more config targets are given
kbuild: remove redundant line from bounds.h/asm-offsets.h
kbuild: merge bounds.h and asm-offsets.h rules
kbuild: Drop support for clean-rule
37e9562453 ("locking/rwsem: Allow conservative optimistic
spinning when readers have lock") forced the default for
optimistic spinning to be disabled if the lock owner was
nil, which makes much sense for readers. However, while
it is not our priority, we can make some optimizations
for write-mostly workloads. We can bail the spinning step
and still be conservative if there are any active tasks,
otherwise there's really no reason not to spin, as the
semaphore is most likely unlocked.
This patch recovers most of a Unixbench 'execl' benchmark
throughput by sleeping less and making better average system
usage:
before:
CPU %user %nice %system %iowait %steal %idle
all 0.60 0.00 8.02 0.00 0.00 91.38
after:
CPU %user %nice %system %iowait %steal %idle
all 1.22 0.00 70.18 0.00 0.00 28.60
Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Jason Low <jason.low2@hp.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Michel Lespinasse <walken@google.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Link: http://lkml.kernel.org/r/1422609267-15102-6-git-send-email-dave@stgolabs.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
When readers hold the semaphore, the ->owner is nil. As such,
and unlike mutexes, '!owner' does not necessarily imply that
the lock is free. This will cause writers to potentially spin
excessively as they've been mislead to thinking they have a
chance of acquiring the lock, instead of blocking.
This patch therefore enhances the counter check when the owner
is not set by the time we've broken out of the loop. Otherwise
we can return true as a new owner has the lock and thus we want
to continue spinning. While at it, we can make rwsem_spin_on_owner()
less ambiguos and return right away under need_resched conditions.
Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Jason Low <jason.low2@hp.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Michel Lespinasse <walken@google.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Link: http://lkml.kernel.org/r/1422609267-15102-5-git-send-email-dave@stgolabs.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
In order to optimize the spinning step, we need to set the lock
owner as soon as the lock is acquired; after a successful counter
cmpxchg operation, that is. This is particularly useful as rwsems
need to set the owner to nil for readers, so there is a greater
chance of falling out of the spinning. Currently we only set the
owner much later in the game, in the more generic level -- latency
can be specially bad when waiting for a node->next pointer when
releasing the osq in up_write calls.
As such, update the owner inside rwsem_try_write_lock (when the
lock is obtained after blocking) and rwsem_try_write_lock_unqueued
(when the lock is obtained while spinning). This requires creating
a new internal rwsem.h header to share the owner related calls.
Also cleanup some headers for mutex and rwsem.
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Jason Low <jason.low2@hp.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Michel Lespinasse <walken@google.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Link: http://lkml.kernel.org/r/1422609267-15102-4-git-send-email-dave@stgolabs.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
The need for the smp_mb() in __rwsem_do_wake() should be
properly documented. Applies to both xadd and spinlock
variants.
Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Jason Low <jason.low2@hp.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Michel Lespinasse <walken@google.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Link: http://lkml.kernel.org/r/1422609267-15102-3-git-send-email-dave@stgolabs.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
attach_to_pi_owner() checks p->mm to prevent attaching to kthreads and
this looks doubly wrong:
1. It should actually check PF_KTHREAD, kthread can do use_mm().
2. If this task is not kthread and it is actually the lock owner we can
wrongly return -EPERM instead of -ESRCH or retry-if-EAGAIN.
And note that this wrong EPERM is the likely case unless the exiting
task is (auto)reaped quickly, we check ->mm before PF_EXITING.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Darren Hart <darren@dvhart.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Jerome Marchand <jmarchan@redhat.com>
Cc: Larry Woodman <lwoodman@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mateusz Guzik <mguzik@redhat.com>
Link: http://lkml.kernel.org/r/20150202140536.GA26406@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
As suggested by Davidlohr, we could refactor mutex_spin_on_owner().
Currently, we split up owner_running() with mutex_spin_on_owner().
When the owner changes, we make duplicate owner checks which are not
necessary. It also makes the code a bit obscure as we are using a
second check to figure out why we broke out of the loop.
This patch modifies it such that we remove the owner_running() function
and the mutex_spin_on_owner() loop directly checks for if the owner changes,
if the owner is not running, or if we need to reschedule. If the owner
changes, we break out of the loop and return true. If the owner is not
running or if we need to reschedule, then break out of the loop and return
false.
Suggested-by: Davidlohr Bueso <dave@stgolabs.net>
Signed-off-by: Jason Low <jason.low2@hp.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Aswin Chandramouleeswaran <aswin@hp.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: chegu_vinod@hp.com
Cc: tglx@linutronix.de
Link: http://lkml.kernel.org/r/1422914367-5574-3-git-send-email-jason.low2@hp.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
In the mutex_spin_on_owner(), we return true only if lock->owner == NULL.
This was beneficial in situations where there were multiple threads
simultaneously spinning for the mutex. If another thread got the lock
while other spinner(s) were also doing mutex_spin_on_owner(), then the
other spinners would stop spinning. This workaround helped reduce the
chance that many spinners were simultaneously spinning for the mutex
which can help reduce contention in highly contended cases.
However, recent changes were made to the optimistic spinning code such
that instead of having all spinners simultaneously spin for the mutex,
we queue the spinners with an MCS lock such that only one thread spins
for the mutex at a time. Furthermore, the OSQ optimizations ensure that
spinners in the queue will stop waiting if it needs to reschedule.
Now, we don't have to worry about multiple threads spinning on owner
at the same time, and if lock->owner is not NULL at this point, it likely
means another thread happens to obtain the lock in the fastpath. In this
case, it would make sense for the spinner to continue spinning as long
as the spinner doesn't need to schedule and the mutex owner is running.
This patch changes this so that mutex_spin_on_owner() returns true when
the lock owner changes, which means a thread will only stop spinning
if it either needs to reschedule or if the lock owner is not running.
We saw up to a 5% performance improvement in the fserver workload with
this patch.
Signed-off-by: Jason Low <jason.low2@hp.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Davidlohr Bueso <dave@stgolabs.net>
Cc: Aswin Chandramouleeswaran <aswin@hp.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: chegu_vinod@hp.com
Cc: tglx@linutronix.de
Link: http://lkml.kernel.org/r/1422914367-5574-2-git-send-email-jason.low2@hp.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Setting the root group's cpu.rt_runtime_us to 0 is a bad thing; it
would disallow the kernel creating RT tasks.
One can of course still set it to 1, which will (likely) still wreck
your kernel, but at least make it clear that setting it to 0 is not
good.
Collect both sanity checks into the one place while we're there.
Suggested-by: Zefan Li <lizefan@huawei.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/20150209112715.GO24151@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Because task_group() uses a cache of autogroup_task_group(), whose
output depends on sched_class, switching classes can generate
problems.
In particular, when started as fair, the cache points to the
autogroup, so when switching to RT the tg_rt_schedulable() test fails
for every cpu.rt_{runtime,period}_us change because now the autogroup
has tasks and no runtime.
Furthermore, going back to the previous semantics of varying
task_group() with sched_class has the down-side that the sched_debug
output varies as well, even though the task really is in the
autogroup.
Therefore add an autogroup exception to tg_has_rt_tasks() -- such that
both (all) task_group() usages in sched/core now have one. And remove
all the remnants of the variable task_group() output.
Reported-by: Zefan Li <lizefan@huawei.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <umgwanakikbuti@gmail.com>
Cc: Stefan Bader <stefan.bader@canonical.com>
Fixes: 8323f26ce3 ("sched: Fix race in task_group()")
Link: http://lkml.kernel.org/r/20150209112237.GR5029@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Additional validation of adjtimex freq values to avoid
potential multiplication overflows were added in commit
5e5aeb4367 (time: adjtimex: Validate the ADJ_FREQUENCY values)
Unfortunately the patch used LONG_MAX/MIN instead of
LLONG_MAX/MIN, which was fine on 64-bit systems, but being
much smaller on 32-bit systems caused false positives
resulting in most direct frequency adjustments to fail w/
EINVAL.
ntpd only does direct frequency adjustments at startup, so
the issue was not as easily observed there, but other time
sync applications like ptpd and chrony were more effected by
the bug.
See bugs:
https://bugzilla.kernel.org/show_bug.cgi?id=92481https://bugzilla.redhat.com/show_bug.cgi?id=1188074
This patch changes the checks to use LLONG_MAX for
clarity, and additionally the checks are disabled
on 32-bit systems since LLONG_MAX/PPM_SCALE is always
larger then the 32-bit long freq value, so multiplication
overflows aren't possible there.
Reported-by: Josh Boyer <jwboyer@fedoraproject.org>
Reported-by: George Joseph <george.joseph@fairview5.com>
Tested-by: George Joseph <george.joseph@fairview5.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: <stable@vger.kernel.org> # v3.19+
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Sasha Levin <sasha.levin@oracle.com>
Link: http://lkml.kernel.org/r/1423553436-29747-1-git-send-email-john.stultz@linaro.org
[ Prettified the changelog and the comments a bit. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
io_schedule() calls blk_flush_plug() which, depending on the
contents of current->plug, can initiate arbitrary blk-io requests.
Note that this contrasts with blk_schedule_flush_plug() which requires
all non-trivial work to be handed off to a separate thread.
This makes it possible for io_schedule() to recurse, and initiating
block requests could possibly call mempool_alloc() which, in times of
memory pressure, uses io_schedule().
Apart from any stack usage issues, io_schedule() will not behave
correctly when called recursively as delayacct_blkio_start() does
not allow for repeated calls.
So:
- use ->in_iowait to detect recursion. Set it earlier, and restore
it to the old value.
- move the call to "raw_rq" after the call to blk_flush_plug().
As this is some sort of per-cpu thing, we want some chance that
we are on the right CPU
- When io_schedule() is called recurively, use blk_schedule_flush_plug()
which cannot further recurse.
- as this makes io_schedule() a lot more complex and as io_schedule()
must match io_schedule_timeout(), but all the changes in io_schedule_timeout()
and make io_schedule a simple wrapper for that.
Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
[ Moved the now rudimentary io_schedule() into sched.h. ]
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Tony Battersby <tonyb@cybernetics.com>
Link: http://lkml.kernel.org/r/20150213162600.059fffb2@notabene.brown
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Commit de30ec4730 "Remove unnecessary ->wait.lock serialization when
reading completion state" was not correct, without lock/unlock the code
like stop_machine_from_inactive_cpu()
while (!completion_done())
cpu_relax();
can return before complete() finishes its spin_unlock() which writes to
this memory. And spin_unlock_wait().
While at it, change try_wait_for_completion() to use READ_ONCE().
Reported-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reported-by: Davidlohr Bueso <dave@stgolabs.net>
Tested-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
[ Added a comment with the barrier. ]
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Nicholas Mc Guire <der.herr@hofr.at>
Cc: raghavendra.kt@linux.vnet.ibm.com
Cc: waiman.long@hp.com
Fixes: de30ec4730 ("sched/completion: Remove unnecessary ->wait.lock serialization when reading completion state")
Link: http://lkml.kernel.org/r/20150212195913.GA30430@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Since the function graph tracer needs to disable preemption, it might
call preempt_schedule() after reenabling it if something triggered the
need for rescheduling in between.
Therefore we can't trace preempt_schedule() itself because we would
face a function tracing recursion otherwise as the tracer is always
called before PREEMPT_ACTIVE gets set to prevent that recursion. This is
why preempt_schedule() is tagged as "notrace".
But the same issue applies to every function called by preempt_schedule()
before PREEMPT_ACTIVE is actually set. And preempt_schedule_common() is
one such example. Unfortunately we forgot to tag it as notrace as well
and as a result we are encountering tracing recursion since it got
introduced by:
a18b5d0181 ("sched: Fix missing preemption opportunity")
Let's fix that by applying the appropriate function tag to
preempt_schedule_common().
Reported-by: Huang Ying <ying.huang@intel.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/1424110807-15057-1-git-send-email-fweisbec@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
A deadline task may be throttled and dequeued at the same time.
This happens, when it becomes throttled in schedule(), which
is called to go to sleep:
current->state = TASK_INTERRUPTIBLE;
schedule()
deactivate_task()
dequeue_task_dl()
update_curr_dl()
start_dl_timer()
__dequeue_task_dl()
prev->on_rq = 0;
Later the timer fires, but the task is still dequeued:
dl_task_timer()
enqueue_task_dl() /* queues on dl_rq; on_rq remains 0 */
Someone wakes it up:
try_to_wake_up()
enqueue_dl_entity()
BUG_ON(on_dl_rq())
Patch fixes this problem, it prevents queueing !on_rq tasks
on dl_rq.
Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Kirill Tkhai <ktkhai@parallels.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
[ Wrote comment. ]
Cc: Juri Lelli <juri.lelli@arm.com>
Fixes: 1019a359d3 ("sched/deadline: Fix stale yield state")
Link: http://lkml.kernel.org/r/1374601424090314@web4j.yandex.ru
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Kirill reported that a dl task can be throttled and dequeued at the
same time. This happens, when it becomes throttled in schedule(),
which is called to go to sleep:
current->state = TASK_INTERRUPTIBLE;
schedule()
deactivate_task()
dequeue_task_dl()
update_curr_dl()
start_dl_timer()
__dequeue_task_dl()
prev->on_rq = 0;
This invalidates the assumption from commit 0f397f2c90 ("sched/dl:
Fix race in dl_task_timer()"):
"The only reason we don't strictly need ->pi_lock now is because
we're guaranteed to have p->state == TASK_RUNNING here and are
thus free of ttwu races".
And therefore we have to use the full task_rq_lock() here.
This further amends the fact that we forgot to update the rq lock loop
for TASK_ON_RQ_MIGRATE, from commit cca26e8009 ("sched: Teach
scheduler to understand TASK_ON_RQ_MIGRATING state").
Reported-by: Kirill Tkhai <ktkhai@parallels.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Juri Lelli <juri.lelli@arm.com>
Link: http://lkml.kernel.org/r/20150217123139.GN5029@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
There was a wee bit of confusion around the exact ordering here;
clarify things.
Reported-by: Kirill Tkhai <ktkhai@parallels.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/20150217121258.GM5029@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
With task_blocks_on_rt_mutex() returning early -EDEADLK we never
add the waiter to the waitqueue. Later, we try to remove it via
remove_waiter() and go boom in rt_mutex_top_waiter() because
rb_entry() gives a NULL pointer.
( Tested on v3.18-RT where rtmutex is used for regular mutex and I
tried to get one twice in a row. )
Not sure when this started but I guess 397335f004 ("rtmutex: Fix
deadlock detector for real") or commit 3d5c9340d1 ("rtmutex:
Handle deadlock detection smarter").
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: <stable@vger.kernel.org> # for v3.16 and later kernels
Link: http://lkml.kernel.org/r/1424187823-19600-1-git-send-email-bigeasy@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Pull getname/putname updates from Al Viro:
"Rework of getname/getname_kernel/etc., mostly from Paul Moore. Gets
rid of quite a pile of kludges between namei and audit..."
* 'getname2' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
audit: replace getname()/putname() hacks with reference counters
audit: fix filename matching in __audit_inode() and __audit_inode_child()
audit: enable filename recording via getname_kernel()
simpler calling conventions for filename_mountpoint()
fs: create proper filename objects using getname_kernel()
fs: rework getname_kernel to handle up to PATH_MAX sized filenames
cut down the number of do_path_lookup() callers
Pull misc VFS updates from Al Viro:
"This cycle a lot of stuff sits on topical branches, so I'll be sending
more or less one pull request per branch.
This is the first pile; more to follow in a few. In this one are
several misc commits from early in the cycle (before I went for
separate branches), plus the rework of mntput/dput ordering on umount,
switching to use of fs_pin instead of convoluted games in
namespace_unlock()"
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
switch the IO-triggering parts of umount to fs_pin
new fs_pin killing logics
allow attaching fs_pin to a group not associated with some superblock
get rid of the second argument of acct_kill()
take count and rcu_head out of fs_pin
dcache: let the dentry count go down to zero without taking d_lock
pull bumping refcount into ->kill()
kill pin_put()
mode_t whack-a-mole: chelsio
file->f_path.dentry is pinned down for as long as the file is open...
get rid of lustre_dump_dentry()
gut proc_register() a bit
kill d_validate()
ncpfs: get rid of d_validate() nonsense
selinuxfs: don't open-code d_genocide()
Merge yet more updates from Andrew Morton:
- a pile of minor fs fixes and cleanups
- kexec updates
- random misc fixes in various places: vmcore, rbtree, eventfd, ipc, seccomp.
- a series of python-based kgdb helper scripts
* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (58 commits)
seccomp: cap SECCOMP_RET_ERRNO data to MAX_ERRNO
samples/seccomp: improve label helper
ipc,sem: use current->state helpers
scripts/gdb: disable pagination while printing from breakpoint handler
scripts/gdb: define maintainer
scripts/gdb: convert CpuList to generator function
scripts/gdb: convert ModuleList to generator function
scripts/gdb: use a generator instead of iterator for task list
scripts/gdb: ignore byte-compiled python files
scripts/gdb: port to python3 / gdb7.7
scripts/gdb: add basic documentation
scripts/gdb: add lx-lsmod command
scripts/gdb: add class to iterate over CPU masks
scripts/gdb: add lx_current convenience function
scripts/gdb: add internal helper and convenience function for per-cpu lookup
scripts/gdb: add get_gdbserver_type helper
scripts/gdb: add internal helper and convenience function to retrieve thread_info
scripts/gdb: add is_target_arch helper
scripts/gdb: add helper and convenience function to look up tasks
scripts/gdb: add task iteration class
...
The value resulting from the SECCOMP_RET_DATA mask could exceed MAX_ERRNO
when setting errno during a SECCOMP_RET_ERRNO filter action. This makes
sure we have a reliable value being set, so that an invalid errno will not
be ignored by userspace.
Signed-off-by: Kees Cook <keescook@chromium.org>
Reported-by: Dmitry V. Levin <ldv@altlinux.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Will Drewry <wad@chromium.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This provides a reliable breakpoint target, required for automatic symbol
loading via the gdb helper command 'lx-symbols'.
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Acked-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Jason Wessel <jason.wessel@windriver.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Ben Widawsky <ben@bwidawsk.net>
Cc: Borislav Petkov <bp@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Simplify the code around one of the conditionals in the kexec_load syscall
routine.
The original code was confusing with a redundant check on KEXEC_ON_CRASH
and comments outside of the conditional block. This change switches the
order of the conditional check, and cleans up the comments for the
conditional. There is no functional change to the code.
Signed-off-by: Geoff Levand <geoff@infradead.org>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Maximilian Attems <max@stro.at>
Cc: Michal Marek <mmarek@suse.cz>
Cc: Paul Bolle <pebolle@tiscali.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
struct kimage has a member destination which is used to store the real
destination address of each page when load segment from user space buffer
to kernel. But we never retrieve the value stored in kimage->destination,
so this member variable in kimage and its assignment operation are
redundent code.
I guess for_each_kimage_entry just does the work that kimage->destination
is expected to do.
So in this patch just make a cleanup to remove it.
Signed-off-by: Baoquan He <bhe@redhat.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Call __set_current_state() instead of assigning the new state directly.
These interfaces also aid CONFIG_DEBUG_ATOMIC_SLEEP environments, keeping
track of who changed the state.
Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Commit 84c751bd4a ("ptrace: add ability to retrieve signals without
removing from a queue (v4)") includes <linux/compat.h> globally in
ptrace.c
This patch removes inclusion under if defined CONFIG_COMPAT.
Signed-off-by: Fabian Frederick <fabf@skynet.be>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Till now suspend-to-idle has not been able to save much more energy
than runtime PM because of timer interrupts that periodically bring
CPUs out of idle while they are waiting for a wakeup interrupt. Of
course, the timer interrupts are not wakeup ones, so the handling of
them can be deferred until a real wakeup interrupt happens, but at
the same time we don't want to mass-expire timers at that point.
The solution is to suspend the entire timekeeping when the last CPU
is entering an idle state and resume it when the first CPU goes out
of idle. That has to be done with care, though, so as to avoid
accessing suspended clocksources etc. end we need extra support
from idle drivers for that.
This series of commits adds support for quiescing timers during
suspend-to-idle and adds the requisite callbacks to intel_idle
and the ACPI cpuidle driver.
/
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Merge tag 'suspend-to-idle-3.20-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm
Pull suspend-to-idle updates from Rafael Wysocki:
"Suspend-to-idle timer quiescing support for v3.20-rc1
Until now suspend-to-idle has not been able to save much more energy
than runtime PM because of timer interrupts that periodically bring
CPUs out of idle while they are waiting for a wakeup interrupt. Of
course, the timer interrupts are not wakeup ones, so the handling of
them can be deferred until a real wakeup interrupt happens, but at the
same time we don't want to mass-expire timers at that point.
The solution is to suspend the entire timekeeping when the last CPU is
entering an idle state and resume it when the first CPU goes out of
idle. That has to be done with care, though, so as to avoid accessing
suspended clocksources etc. end we need extra support from idle
drivers for that.
This series of commits adds support for quiescing timers during
suspend-to-idle and adds the requisite callbacks to intel_idle and the
ACPI cpuidle driver"
* tag 'suspend-to-idle-3.20-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm:
ACPI / idle: Implement ->enter_freeze callback routine
intel_idle: Add ->enter_freeze callbacks
PM / sleep: Make it possible to quiesce timers during suspend-to-idle
timekeeping: Make it safe to use the fast timekeeper while suspended
timekeeping: Pass readout base to update_fast_timekeeper()
PM / sleep: Re-implement suspend-to-idle handling
Pull irqchip updates from Ingo Molnar:
"Various irqchip driver updates, plus a genirq core update that allows
the initial spreading of irqs amonst CPUs without having to do it from
user-space"
* 'irq-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
genirq: Fix null pointer reference in irq_set_affinity_hint()
irqchip: gic: Allow interrupt level to be set for PPIs
irqchip: mips-gic: Handle pending interrupts once in __gic_irq_dispatch()
irqchip: Conexant CX92755 interrupts controller driver
irqchip: Devicetree: document Conexant Digicolor irq binding
irqchip: omap-intc: Remove unused legacy interface for omap2
irqchip: omap-intc: Fix support for dm814 and dm816
irqchip: mtk-sysirq: Get irq number from register resource size
irqchip: renesas-intc-irqpin: r8a7779 IRLM setup support
genirq: Set initial affinity in irq_set_affinity_hint()
Pull x86 perf updates from Ingo Molnar:
"This series tightens up RDPMC permissions: currently even highly
sandboxed x86 execution environments (such as seccomp) have permission
to execute RDPMC, which may leak various perf events / PMU state such
as timing information and other CPU execution details.
This 'all is allowed' RDPMC mode is still preserved as the
(non-default) /sys/devices/cpu/rdpmc=2 setting. The new default is
that RDPMC access is only allowed if a perf event is mmap-ed (which is
needed to correctly interpret RDPMC counter values in any case).
As a side effect of these changes CR4 handling is cleaned up in the
x86 code and a shadow copy of the CR4 value is added.
The extra CR4 manipulation adds ~ <50ns to the context switch cost
between rdpmc-capable and rdpmc-non-capable mms"
* 'perf-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
perf/x86: Add /sys/devices/cpu/rdpmc=2 to allow rdpmc for all tasks
perf/x86: Only allow rdpmc if a perf_event is mapped
perf: Pass the event to arch_perf_update_userpage()
perf: Add pmu callbacks to track event mapping and unmapping
x86: Add a comment clarifying LDT context switching
x86: Store a per-cpu shadow copy of CR4
x86: Clean up cr4 manipulation
Jason Low