Re: Patch: linux-2.5.8-pre1/kernel/exit.c change caused BUG() at boot time

From: Linus Torvalds (torvalds@transmeta.com)
Date: Thu Apr 04 2002 - 14:14:33 EST


On 4 Apr 2002, Robert Love wrote:
>
> Thanks for the CC. I've been looking into this problem. I am not too
> sure why we require protection from concurrency via preemption and not
> via SMP. In other words, why are we SMP-safe but not preempt-safe here.
>
> I don't really have an answer.

The answer is that preempt_schedule() illegally sets

        current->state = TASK_RUNNING;

without asking the process whether that's ok. The SMP code never does
anything like that.

                Linus

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