Commit Graph

7 Commits

Author SHA1 Message Date
Paul E. McKenney d9f1bb6ad7 rcu: Make rcu_read_lock_sched_held() take boot time into account
Before the scheduler starts, all tasks are non-preemptible by
definition. So, during that time, rcu_read_lock_sched_held()
needs to always return "true".  This patch makes that be so.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: laijs@cn.fujitsu.com
Cc: dipankar@in.ibm.com
Cc: mathieu.desnoyers@polymtl.ca
Cc: josh@joshtriplett.org
Cc: dvhltc@us.ibm.com
Cc: niv@us.ibm.com
Cc: peterz@infradead.org
Cc: rostedt@goodmis.org
Cc: Valdis.Kletnieks@vt.edu
Cc: dhowells@redhat.com
LKML-Reference: <1267135607-7056-2-git-send-email-paulmck@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-02-26 08:20:46 +01:00
Paul E. McKenney bf66f18e79 rcu: Add force_quiescent_state() testing to rcutorture
Add force_quiescent_state() testing to rcutorture, with a
separate thread that repeatedly invokes force_quiescent_state()
in bursts. This can greatly increase the probability of
encountering certain types of race conditions.

Suggested-by: Josh Triplett <josh@joshtriplett.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: laijs@cn.fujitsu.com
Cc: dipankar@in.ibm.com
Cc: mathieu.desnoyers@polymtl.ca
Cc: josh@joshtriplett.org
Cc: dvhltc@us.ibm.com
Cc: niv@us.ibm.com
Cc: peterz@infradead.org
Cc: rostedt@goodmis.org
Cc: Valdis.Kletnieks@vt.edu
Cc: dhowells@redhat.com
LKML-Reference: <1262646551116-git-send-email->
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-01-13 09:06:05 +01:00
Frederic Weisbecker 234da7bcdc sched: Teach might_sleep() about preemptible RCU
In practice, it is harmless to voluntarily sleep in a
rcu_read_lock() section if we are running under preempt rcu, but
it is illegal if we build a kernel running non-preemptable rcu.

Currently, might_sleep() doesn't notice sleepable operations
under rcu_read_lock() sections if we are running under
preemptable rcu because preempt_count() is left untouched after
rcu_read_lock() in this case. But we want developers who test
their changes under such config to notice the "sleeping while
atomic" issues.

So we add rcu_read_lock_nesting to prempt_count() in
might_sleep() checks.

[ v2: Handle rcu-tiny ]
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
LKML-Reference: <1260991265-8451-1-git-send-regression-fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-12-17 09:46:44 +01:00
Paul E. McKenney 6ebb237bec rcu: Re-arrange code to reduce #ifdef pain
Remove #ifdefs from kernel/rcupdate.c and
include/linux/rcupdate.h by moving code to
include/linux/rcutiny.h, include/linux/rcutree.h, and
kernel/rcutree.c.

Also remove some definitions that are no longer used.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: laijs@cn.fujitsu.com
Cc: dipankar@in.ibm.com
Cc: mathieu.desnoyers@polymtl.ca
Cc: josh@joshtriplett.org
Cc: dvhltc@us.ibm.com
Cc: niv@us.ibm.com
Cc: peterz@infradead.org
Cc: rostedt@goodmis.org
Cc: Valdis.Kletnieks@vt.edu
Cc: dhowells@redhat.com
LKML-Reference: <1258908830885-git-send-email->
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-11-22 18:58:16 +01:00
Paul E. McKenney 9f680ab414 rcu: Eliminate unneeded function wrapping
The functions rcu_init() is a wrapper for __rcu_init(), and also
sets up the CPU-hotplug notifier for rcu_barrier_cpu_hotplug().
But TINY_RCU doesn't need CPU-hotplug notification, and the
rcu_barrier_cpu_hotplug() is a simple wrapper for
rcu_cpu_notify().

So push rcu_init() out to kernel/rcutree.c and kernel/rcutiny.c
and get rid of the wrapper function rcu_barrier_cpu_hotplug().

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: laijs@cn.fujitsu.com
Cc: dipankar@in.ibm.com
Cc: mathieu.desnoyers@polymtl.ca
Cc: josh@joshtriplett.org
Cc: dvhltc@us.ibm.com
Cc: niv@us.ibm.com
Cc: peterz@infradead.org
Cc: rostedt@goodmis.org
Cc: Valdis.Kletnieks@vt.edu
Cc: dhowells@redhat.com
LKML-Reference: <12589088302320-git-send-email->
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-11-22 18:58:16 +01:00
Ingo Molnar 4ce5b90340 rcu: Do tiny cleanups in rcutiny
No change in functionality - just straighten out a few small
stylistic details.

Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: laijs@cn.fujitsu.com
Cc: dipankar@in.ibm.com
Cc: mathieu.desnoyers@polymtl.ca
Cc: dvhltc@us.ibm.com
Cc: niv@us.ibm.com
Cc: peterz@infradead.org
Cc: rostedt@goodmis.org
Cc: Valdis.Kletnieks@vt.edu
Cc: avi@redhat.com
Cc: mtosatti@redhat.com
LKML-Reference: <12565226351355-git-send-email->
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-10-26 09:40:40 +01:00
Paul E. McKenney 9b1d82fa16 rcu: "Tiny RCU", The Bloatwatch Edition
This patch is a version of RCU designed for !SMP provided for a
small-footprint RCU implementation.  In particular, the
implementation of synchronize_rcu() is extremely lightweight and
high performance. It passes rcutorture testing in each of the
four relevant configurations (combinations of NO_HZ and PREEMPT)
on x86.  This saves about 1K bytes compared to old Classic RCU
(which is no longer in mainline), and more than three kilobytes
compared to Hierarchical RCU (updated to 2.6.30):

	CONFIG_TREE_RCU:

	   text	   data	    bss	    dec	    filename
	    183       4       0     187     kernel/rcupdate.o
	   2783     520      36    3339     kernel/rcutree.o
				   3526 Total (vs 4565 for v7)

	CONFIG_TREE_PREEMPT_RCU:

	   text	   data	    bss	    dec	    filename
	    263       4       0     267     kernel/rcupdate.o
	   4594     776      52    5422     kernel/rcutree.o
	   			   5689 Total (6155 for v7)

	CONFIG_TINY_RCU:

	   text	   data	    bss	    dec	    filename
	     96       4       0     100     kernel/rcupdate.o
	    734      24       0     758     kernel/rcutiny.o
	    			    858 Total (vs 848 for v7)

The above is for x86.  Your mileage may vary on other platforms.
Further compression is possible, but is being procrastinated.

Changes from v7 (http://lkml.org/lkml/2009/10/9/388)

o	Apply Lai Jiangshan's review comments (aside from
might_sleep() 	in synchronize_sched(), which is covered by SMP builds).

o	Fix up expedited primitives.

Changes from v6 (http://lkml.org/lkml/2009/9/23/293).

o	Forward ported to put it into the 2.6.33 stream.

o	Added lockdep support.

o	Make lightweight rcu_barrier.

Changes from v5 (http://lkml.org/lkml/2009/6/23/12).

o	Ported to latest pre-2.6.32 merge window kernel.

	- Renamed rcu_qsctr_inc() to rcu_sched_qs().
	- Renamed rcu_bh_qsctr_inc() to rcu_bh_qs().
	- Provided trivial rcu_cpu_notify().
	- Provided trivial exit_rcu().
	- Provided trivial rcu_needs_cpu().
	- Fixed up the rcu_*_enter/exit() functions in linux/hardirq.h.

o	Removed the dependence on EMBEDDED, with a view to making
	TINY_RCU default for !SMP at some time in the future.

o	Added (trivial) support for expedited grace periods.

Changes from v4 (http://lkml.org/lkml/2009/5/2/91) include:

o	Squeeze the size down a bit further by removing the
	->completed field from struct rcu_ctrlblk.

o	This permits synchronize_rcu() to become the empty function.
	Previous concerns about rcutorture were unfounded, as
	rcutorture correctly handles a constant value from
	rcu_batches_completed() and rcu_batches_completed_bh().

Changes from v3 (http://lkml.org/lkml/2009/3/29/221) include:

o	Changed rcu_batches_completed(), rcu_batches_completed_bh()
	rcu_enter_nohz(), rcu_exit_nohz(), rcu_nmi_enter(), and
	rcu_nmi_exit(), to be static inlines, as suggested by David
	Howells.  Doing this saves about 100 bytes from rcutiny.o.
	(The numbers between v3 and this v4 of the patch are not directly
	comparable, since they are against different versions of Linux.)

Changes from v2 (http://lkml.org/lkml/2009/2/3/333) include:

o	Fix whitespace issues.

o	Change short-circuit "||" operator to instead be "+" in order
to 	fix performance bug noted by "kraai" on LWN.

		(http://lwn.net/Articles/324348/)

Changes from v1 (http://lkml.org/lkml/2009/1/13/440) include:

o	This version depends on EMBEDDED as well as !SMP, as suggested
	by Ingo.

o	Updated rcu_needs_cpu() to unconditionally return zero,
	permitting the CPU to enter dynticks-idle mode at any time.
	This works because callbacks can be invoked upon entry to
	dynticks-idle mode.

o	Paul is now OK with this being included, based on a poll at
the 	Kernel Miniconf at linux.conf.au, where about ten people said
	that they cared about saving 900 bytes on single-CPU systems.

o	Applies to both mainline and tip/core/rcu.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: David Howells <dhowells@redhat.com>
Acked-by: Josh Triplett <josh@joshtriplett.org>
Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: dipankar@in.ibm.com
Cc: mathieu.desnoyers@polymtl.ca
Cc: dvhltc@us.ibm.com
Cc: niv@us.ibm.com
Cc: peterz@infradead.org
Cc: rostedt@goodmis.org
Cc: Valdis.Kletnieks@vt.edu
Cc: avi@redhat.com
Cc: mtosatti@redhat.com
LKML-Reference: <12565226351355-git-send-email->
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-10-26 09:40:29 +01:00