| Message ID | 20190103150104.17128-4-rpenyaev@suse.de (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | use rwlock in order to reduce ep_poll_callback() contention | expand |
diff --git a/fs/eventpoll.c b/fs/eventpoll.c index 3c373a510f65..0122b9147542 100644 --- a/fs/eventpoll.c +++ b/fs/eventpoll.c @@ -1167,14 +1167,7 @@ static int ep_poll_callback(wait_queue_entry_t *wait, unsigned mode, int sync, v if (epi->next == EP_UNACTIVE_PTR) { epi->next = READ_ONCE(ep->ovflist); WRITE_ONCE(ep->ovflist, epi); - if (epi->ws) { - /* - * Activate ep->ws since epi->ws may get - * deactivated at any time. - */ - __pm_stay_awake(ep->ws); - } - + ep_pm_stay_awake_rcu(epi); } goto out_unlock; }
Original comment "Activate ep->ws since epi->ws may get deactivated at any time" indeed sounds loud, but it is incorrect, because the path where we check epi->ws is a path where insert to ovflist happens, i.e. ep_scan_ready_list() has taken ep->mtx and waits for this callback to finish, thus ep_modify() (which unregisters wakeup source) waits for ep_scan_ready_list(). Here in this patch I simply call ep_pm_stay_awake_rcu(), which is a bit extra for this path (indirectly protected by main ep->mtx, so even rcu is not needed), but I do not want to create another naked __ep_pm_stay_awake() variant only for this particular case, so rcu variant is just better for all the cases. Signed-off-by: Roman Penyaev <rpenyaev@suse.de> Cc: Davidlohr Bueso <dbueso@suse.de> Cc: Jason Baron <jbaron@akamai.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: linux-fsdevel@vger.kernel.org Cc: linux-kernel@vger.kernel.org --- fs/eventpoll.c | 9 +-------- 1 file changed, 1 insertion(+), 8 deletions(-)