Messages in this thread | | | Date | Fri, 15 May 2015 11:22:09 -0700 | Subject | Re: [PATCH 10/23] userfaultfd: add new syscall to provide memory externalization | From | Linus Torvalds <> |
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On Fri, May 15, 2015 at 9:04 AM, Andrea Arcangeli <aarcange@redhat.com> wrote: > > To fix it I added this along a comment:
Ok, this looks good as a explanation/fix for the races (and also as an example of my worry about waitqueue_active() use in general).
However, it now makes me suspect that the optimistic "let's check if they are even active" may not be worth it any more. You're adding a "smp_mb()" in order to avoid taking the real lock. Although I guess there are two locks there (one for each wait-queue) so maybe it's worth it.
Linus
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