From: Oleg Nesterov Date: Fri, 29 Sep 2006 09:01:09 +0000 (-0700) Subject: [PATCH] set EXIT_DEAD state in do_exit(), not in schedule() X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=29b884921634e1e01cbd276e1c9b8fc07a7e4a90;p=GitHub%2FLineageOS%2FG12%2Fandroid_kernel_amlogic_linux-4.9.git [PATCH] set EXIT_DEAD state in do_exit(), not in schedule() schedule() checks PF_DEAD on every context switch and sets ->state = EXIT_DEAD to ensure that the exiting task will be deactivated. Note that this EXIT_DEAD is in fact a "random" value, we can use any bit except normal TASK_XXX values. It is better to set this state in do_exit() along with PF_DEAD flag and remove that check in schedule(). We are safe wrt concurrent try_to_wake_up() (for example ptrace, tkill), it can not change task's ->state: the 'state' argument of try_to_wake_up() can't have EXIT_DEAD bit. And in case when try_to_wake_up() sees a stale value of ->state == TASK_RUNNING it will do nothing. Signed-off-by: Oleg Nesterov Cc: Ingo Molnar Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/kernel/exit.c b/kernel/exit.c index 4a280856acd2..3d759c98fb11 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -957,6 +957,7 @@ fastcall NORET_TYPE void do_exit(long code) preempt_disable(); BUG_ON(tsk->flags & PF_DEAD); tsk->flags |= PF_DEAD; + tsk->state = EXIT_DEAD; schedule(); BUG(); diff --git a/kernel/sched.c b/kernel/sched.c index 155a33da7aa7..e1646b044b69 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -3348,9 +3348,6 @@ need_resched_nonpreemptible: spin_lock_irq(&rq->lock); - if (unlikely(prev->flags & PF_DEAD)) - prev->state = EXIT_DEAD; - switch_count = &prev->nivcsw; if (prev->state && !(preempt_count() & PREEMPT_ACTIVE)) { switch_count = &prev->nvcsw;