diff options
author | Eric Wong <normalperson@yhbt.net> | 2013-01-01 16:20:27 -0500 |
---|---|---|
committer | Linus Torvalds <torvalds@linux-foundation.org> | 2013-01-02 12:16:43 -0500 |
commit | 128dd1759d96ad36c379240f8b9463e8acfd37a1 (patch) | |
tree | ff5a716b9dcd319d203485e9aa86f3512d555fce /mm/mempolicy.c | |
parent | 4a490b78cb7e0e5efa44425df72a9fedc1c36366 (diff) |
epoll: prevent missed events on EPOLL_CTL_MOD
EPOLL_CTL_MOD sets the interest mask before calling f_op->poll() to
ensure events are not missed. Since the modifications to the interest
mask are not protected by the same lock as ep_poll_callback, we need to
ensure the change is visible to other CPUs calling ep_poll_callback.
We also need to ensure f_op->poll() has an up-to-date view of past
events which occured before we modified the interest mask. So this
barrier also pairs with the barrier in wq_has_sleeper().
This should guarantee either ep_poll_callback or f_op->poll() (or both)
will notice the readiness of a recently-ready/modified item.
This issue was encountered by Andreas Voellmy and Junchang(Jason) Wang in:
http://thread.gmane.org/gmane.linux.kernel/1408782/
Signed-off-by: Eric Wong <normalperson@yhbt.net>
Cc: Hans Verkuil <hans.verkuil@cisco.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Davide Libenzi <davidel@xmailserver.org>
Cc: Hans de Goede <hdegoede@redhat.com>
Cc: Mauro Carvalho Chehab <mchehab@infradead.org>
Cc: David Miller <davem@davemloft.net>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andreas Voellmy <andreas.voellmy@yale.edu>
Tested-by: "Junchang(Jason) Wang" <junchang.wang@yale.edu>
Cc: netdev@vger.kernel.org
Cc: linux-fsdevel@vger.kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/mempolicy.c')
0 files changed, 0 insertions, 0 deletions