Messages in this thread | | | Date | Wed, 24 Jun 2020 18:43:20 +0200 | From | Oleg Nesterov <> | Subject | Re: wait_on_page_bit_common(TASK_KILLABLE, EXCLUSIVE) can miss wakeup? |
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On 06/24, Linus Torvalds wrote: > > That said, I'm not entirely happy with your patch.
Neither me,
> The real problem, I feel, is that > > if (likely(bit_is_set)) > io_schedule(); > > anti-pattern. Without that, we wouldn't have the bug. > > Normally, we'd be TASK_RUNNING in this sequence, but because we might > skip io_schedule(), we can still be in a "sleeping" state here and be > "woken up" between that bit setting and the signal check.
Ah.
And now it _seems_ to me that even if io_schedule() is called try_to_wake_up() can "falsely" succed if signal_pending_state() is true, even if __schedule() won't block in this case.
But I am sure I missed something else. I spent to much time reading the random code paths today, I'll return tomorrow.
Oleg.
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