Messages in this thread Patch in this message | | | Date | Sat, 26 Aug 2006 23:17:41 +0400 | From | Oleg Nesterov <> | Subject | [PATCH 1/3] set EXIT_DEAD state in do_exit(), not in schedule() |
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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 <oleg@tv-sign.ru>
--- 2.6.18-rc4/kernel/exit.c~1_state 2006-08-19 23:47:01.000000000 +0400 +++ 2.6.18-rc4/kernel/exit.c 2006-08-26 20:38:04.000000000 +0400 @@ -957,6 +957,7 @@ fastcall NORET_TYPE void do_exit(long co preempt_disable(); BUG_ON(tsk->flags & PF_DEAD); tsk->flags |= PF_DEAD; + tsk->state = EXIT_DEAD; schedule(); BUG(); --- 2.6.18-rc4/kernel/sched.c~1_state 2006-08-20 00:37:27.000000000 +0400 +++ 2.6.18-rc4/kernel/sched.c 2006-08-26 20:39:02.000000000 +0400 @@ -3311,9 +3311,6 @@ 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; - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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