* [PATCH] preemptoff tracer: trace the preempt enable at preempt_schedule
@ 2010-11-13 0:24 Todd Poynor
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From: Todd Poynor @ 2010-11-13 0:24 UTC (permalink / raw)
To: linux-kernel; +Cc: srostedt, Todd Poynor
preempt_schedule() uses the _notrace versions of the preemption
disable/enable routines for setting the PREEMPT_ACTIVE flag to avoid
a race condition per commit d1f74e2. This causes the preemptoff
trace to not be properly terminated when the preempted thread is
rescheduled. Since the original fix only converted the preempt
re-enable to use the _notrace version for symmetry, call the tracing
version instead. The corresponding preemptoff start will be
traced by the preempt_disable() in schedule(), although this may
be relying on a fragile state of affairs, and it may be best to also
add a direct call to trace a preempt disable after preemption is
safely disabled and the race avoided.
Signed-off-by: Todd Poynor <toddpoynor@google.com>
---
kernel/sched.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)
diff --git a/kernel/sched.c b/kernel/sched.c
index aa14a56..de83e30 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -4041,7 +4041,7 @@ asmlinkage void __sched notrace preempt_schedule(void)
do {
add_preempt_count_notrace(PREEMPT_ACTIVE);
schedule();
- sub_preempt_count_notrace(PREEMPT_ACTIVE);
+ sub_preempt_count(PREEMPT_ACTIVE);
/*
* Check again in case we missed a preemption opportunity
--
1.7.3.1
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2010-11-13 0:24 [PATCH] preemptoff tracer: trace the preempt enable at preempt_schedule Todd Poynor
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