From b22366cd54c6fe05db426f20adb10f461c19ec06 Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Sun, 24 Feb 2013 12:59:30 +0100 Subject: [PATCH] context_tracking: Restore preempted context state after preempt_schedule_irq() From the context tracking POV, preempt_schedule_irq() behaves pretty much like an exception: It can be called anytime and schedule another task. But currently it doesn't restore the context tracking state of the preempted code on preempt_schedule_irq() return. As a result, if preempt_schedule_irq() is called in the tiny frame between user_enter() and the actual return to userspace, we resume userspace with the wrong context tracking state. Fix this by using exception_enter/exit() which are a perfect fit for this kind of issue. Signed-off-by: Frederic Weisbecker Cc: Li Zhong Cc: Kevin Hilman Cc: Mats Liljegren Cc: Peter Zijlstra Cc: Ingo Molnar Cc: Steven Rostedt Cc: Namhyung Kim Cc: Andrew Morton Cc: Thomas Gleixner Cc: Paul E. McKenney --- kernel/sched/core.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 7f12624a393c..af7a8c84b797 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -3082,11 +3082,13 @@ EXPORT_SYMBOL(preempt_schedule); asmlinkage void __sched preempt_schedule_irq(void) { struct thread_info *ti = current_thread_info(); + enum ctx_state prev_state; /* Catch callers which need to be fixed */ BUG_ON(ti->preempt_count || !irqs_disabled()); - user_exit(); + prev_state = exception_enter(); + do { add_preempt_count(PREEMPT_ACTIVE); local_irq_enable(); @@ -3100,6 +3102,8 @@ asmlinkage void __sched preempt_schedule_irq(void) */ barrier(); } while (need_resched()); + + exception_exit(prev_state); } #endif /* CONFIG_PREEMPT */