Commit-ID: b99def8b961448f5b9a550dddeeb718e3975e7a6 Gitweb: http://git.kernel.org/tip/b99def8b961448f5b9a550dddeeb718e3975e7a6 Author: Peter Zijlstra <peterz@xxxxxxxxxxxxx> AuthorDate: Mon, 28 Sep 2015 18:02:03 +0200 Committer: Ingo Molnar <mingo@xxxxxxxxxx> CommitDate: Tue, 6 Oct 2015 17:08:13 +0200 sched/core: Rework TASK_DEAD preemption exception TASK_DEAD is special in that the final schedule call from do_exit() must be done with preemption disabled. This means we end up scheduling with a preempt_count() higher than usual (3 instead of the 'expected' 2). Since future patches will want to rely on an invariant preempt_count() value during schedule, fix this up. Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> Reviewed-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Reviewed-by: Frederic Weisbecker <fweisbec@xxxxxxxxx> Reviewed-by: Steven Rostedt <rostedt@xxxxxxxxxxx> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Cc: Mike Galbraith <efault@xxxxxx> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Cc: linux-kernel@xxxxxxxxxxxxxxx Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx> --- kernel/sched/core.c | 19 +++++++++++++------ 1 file changed, 13 insertions(+), 6 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 88a4254..530fe8ba 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -2949,12 +2949,8 @@ static inline void schedule_debug(struct task_struct *prev) #ifdef CONFIG_SCHED_STACK_END_CHECK BUG_ON(unlikely(task_stack_end_corrupted(prev))); #endif - /* - * Test if we are atomic. Since do_exit() needs to call into - * schedule() atomically, we ignore that path. Otherwise whine - * if we are scheduling when we should not. - */ - if (unlikely(in_atomic_preempt_off() && prev->state != TASK_DEAD)) + + if (unlikely(in_atomic_preempt_off())) __schedule_bug(prev); rcu_sleep_check(); @@ -3053,6 +3049,17 @@ static void __sched __schedule(void) rcu_note_context_switch(); prev = rq->curr; + /* + * do_exit() calls schedule() with preemption disabled as an exception; + * however we must fix that up, otherwise the next task will see an + * inconsistent (higher) preempt count. + * + * It also avoids the below schedule_debug() test from complaining + * about this. + */ + if (unlikely(prev->state == TASK_DEAD)) + preempt_enable_no_resched_notrace(); + schedule_debug(prev); if (sched_feat(HRTICK)) -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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