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sched/core: More notrace annotations
preempt_schedule_common() is marked notrace, but it does not use _notrace() preempt_count functions and __schedule() is also not marked notrace, which means that its perfectly possible to end up in the tracer from preempt_schedule_common(). Steve says: | Yep, there's some history to this. This was originally the issue that | caused function tracing to go into infinite recursion. But now we have | preempt_schedule_notrace(), which is used by the function tracer, and | that function must not be traced till preemption is disabled. | | Now if function tracing is running and we take an interrupt when | NEED_RESCHED is set, it calls | | preempt_schedule_common() (not traced) | | But then that calls preempt_disable() (traced) | | function tracer calls preempt_disable_notrace() followed by | preempt_enable_notrace() which will see NEED_RESCHED set, and it will | call preempt_schedule_notrace(), which stops the recursion, but | still calls __schedule() here, and that means when we return, we call | the __schedule() from preempt_schedule_common(). | | That said, I prefer this patch. Preemption is disabled before calling | __schedule(), and we get rid of a one round recursion with the | scheduler. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Steven Rostedt <rostedt@goodmis.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mike Galbraith <efault@gmx.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
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1 changed files with 3 additions and 3 deletions
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@ -3057,7 +3057,7 @@ pick_next_task(struct rq *rq, struct task_struct *prev)
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*
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* WARNING: must be called with preemption disabled!
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*/
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static void __sched __schedule(bool preempt)
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static void __sched notrace __schedule(bool preempt)
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{
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struct task_struct *prev, *next;
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unsigned long *switch_count;
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@ -3203,9 +3203,9 @@ void __sched schedule_preempt_disabled(void)
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static void __sched notrace preempt_schedule_common(void)
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{
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do {
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preempt_disable();
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preempt_disable_notrace();
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__schedule(true);
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sched_preempt_enable_no_resched();
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preempt_enable_no_resched_notrace();
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/*
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* Check again in case we missed a preemption opportunity
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