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 a18b5d01819235629289212ad428a5ee2b40f0d9
("sched: Fix missing preemption opportunity").
Let's fix that by applying the appropriate function tag to
preempt_schedule_common().
Reported-by: Huang Ying <[email protected]>
Acked-by: Steven Rostedt <[email protected]>
Cc: Huang Ying <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Steven Rostedt <[email protected]>
Signed-off-by: Frederic Weisbecker <[email protected]>
---
kernel/sched/core.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 13049aa..683e850 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2899,7 +2899,7 @@ void __sched schedule_preempt_disabled(void)
preempt_disable();
}
-static void preempt_schedule_common(void)
+static void __sched notrace preempt_schedule_common(void)
{
do {
__preempt_count_add(PREEMPT_ACTIVE);
--
2.1.4
Commit-ID: 06b1f8083d6ed379ec1207a96339f23e8f7abfcf
Gitweb: http://git.kernel.org/tip/06b1f8083d6ed379ec1207a96339f23e8f7abfcf
Author: Frederic Weisbecker <[email protected]>
AuthorDate: Mon, 16 Feb 2015 19:20:07 +0100
Committer: Ingo Molnar <[email protected]>
CommitDate: Wed, 18 Feb 2015 14:27:38 +0100
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 <[email protected]>
Signed-off-by: Frederic Weisbecker <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Acked-by: Steven Rostedt <[email protected]>
Cc: Linus Torvalds <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>
---
kernel/sched/core.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index f77acd9..c314000 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2839,7 +2839,7 @@ void __sched schedule_preempt_disabled(void)
preempt_disable();
}
-static void preempt_schedule_common(void)
+static void __sched notrace preempt_schedule_common(void)
{
do {
__preempt_count_add(PREEMPT_ACTIVE);