userfaultfd: avoid missing wakeups during refile in userfaultfd_read

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During the refile in userfaultfd_read both waitqueues could look empty to
the lockless wake_userfault().  Use a seqcount to prevent this false
negative that could leave an userfault blocked.

Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

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Andrea Arcangeli 2015-09-04 15:47:23 -07:00 • committed by Linus Torvalds

parent 230c92a879

commit 2c5b7e1be7

1 changed files with 24 additions and 2 deletions

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fs/userfaultfd.c

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