Hi,
On Tue, 28 Mar 2006, Oleg Nesterov wrote:
> I also think this is racy.
>
> CPU_0 CPU_1
>
> hrtimer_wakeup:
>
> task = t->task;
> t->task = NULL;
>
> <--- INTERRUPT --->
>
> task is woken by signal,
> do_nanosleep() sees t->task == NULL,
> returns without hrtimer_cancel(),
> and __exits__.
>
> <--- RESUME --->
>
> wake_up_process(task);
>
> Instead of exit(), 'task' can go to TASK_STOPPED or TASK_UNINTERRUPTIBLE
> after return from do_nanosleep(), it will be awakened by hrtimer_wakeup()
> unexpectedly.
Indeed and my original patch did call hrtimer_cancel() unconditionally to
synchronize with a possibly running timer.
Thomas, could you please document it a bit better, when you modify my
patches?
bye, Roman
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