sched: Fix preempt_schedule_common() triggering tracing recursion
authorFrederic Weisbecker <fweisbec@gmail.com>
Mon, 16 Feb 2015 18:20:07 +0000 (19:20 +0100)
committerIngo Molnar <mingo@kernel.org>
Wed, 18 Feb 2015 13:27:38 +0000 (14:27 +0100)
commit06b1f8083d6ed379ec1207a96339f23e8f7abfcf
tree4a26cb052b35a5fa11e7d731d367b3e34bf5cdfa
parenta79ec89fd8459f0de850898f432a2a57d60e64de
sched: Fix preempt_schedule_common() triggering tracing recursion

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:

   a18b5d0181923 ("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>
kernel/sched/core.c