Messages in this thread | | | Date | Tue, 17 Dec 2019 16:23:33 +0100 | From | Oleg Nesterov <> | Subject | Re: [PATCH v2] kernel/exit: do panic earlier to get coredump if global init task exit |
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On 12/17, chenqiwu wrote: > > But in fact, I think atomic_read() > can avoid the racy even if both threads exit in parallel, since it is > an atomic operation forever.
Hmm, not sure I understand. atomic_read() is just READ_ONCE(), it can't be re-ordered but that is all.
How can it avoid the race if it is called before atomic_dec_and_test() ?
Again, suppose that we have 2 exiting threads and signal->live == 2. With your patch each thread does atomic_read() before atomic_dec_and_test(), both threads can observe atomic_read(signal->live) == 2 simply because the counter was not decremented yet.
Oleg.
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