| commit | 128dd1759d96ad36c379240f8b9463e8acfd37a1 | [log] [tgz] |
|---|---|---|
| author | Eric Wong <[email protected]> | Tue Jan 01 21:20:27 2013 +0000 |
| committer | Linus Torvalds <[email protected]> | Wed Jan 02 09:16:43 2013 -0800 |
| tree | ff5a716b9dcd319d203485e9aa86f3512d555fce | |
| 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 <[email protected]> Cc: Hans Verkuil <[email protected]> Cc: Jiri Olsa <[email protected]> Cc: Jonathan Corbet <[email protected]> Cc: Al Viro <[email protected]> Cc: Davide Libenzi <[email protected]> Cc: Hans de Goede <[email protected]> Cc: Mauro Carvalho Chehab <[email protected]> Cc: David Miller <[email protected]> Cc: Eric Dumazet <[email protected]> Cc: Andrew Morton <[email protected]> Cc: Andreas Voellmy <[email protected]> Tested-by: "Junchang(Jason) Wang" <[email protected]> Cc: [email protected] Cc: [email protected] Signed-off-by: Linus Torvalds <[email protected]>