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| author | Peter Zijlstra <peterz@infradead.org> | 2015-09-28 18:02:03 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2015-10-06 17:08:13 +0200 |
| commit | b99def8b961448f5b9a550dddeeb718e3975e7a6 (patch) | |
| tree | 28a9f70f27b02dcbecbdd1e386744f4332e927f9 /kernel/sched | |
| parent | sched/core: Simplify INIT_PREEMPT_COUNT (diff) | |
| download | linux-b99def8b961448f5b9a550dddeeb718e3975e7a6.tar.xz linux-b99def8b961448f5b9a550dddeeb718e3975e7a6.zip | |
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@infradead.org>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <fweisbec@gmail.com>
Reviewed-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>
Diffstat (limited to 'kernel/sched')
| -rw-r--r-- | kernel/sched/core.c | 19 |
1 files changed, 13 insertions, 6 deletions
diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 88a425443ff4..530fe8baa645 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)) |