The patch titled Subject: eventpoll: fix missing wakeup for ovflist in ep_poll_callback has been added to the -mm tree. Its filename is eventpoll-fix-missing-wakeup-for-ovflist-in-ep_poll_callback.patch
This patch should soon appear at http://ozlabs.org/~akpm/mmots/broken-out/eventpoll-fix-missing-wakeup-for-ov... and later at http://ozlabs.org/~akpm/mmotm/broken-out/eventpoll-fix-missing-wakeup-for-ov...
Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next and is updated there every 3-4 working days
------------------------------------------------------ From: Khazhismel Kumykov khazhy@google.com Subject: eventpoll: fix missing wakeup for ovflist in ep_poll_callback
In the event that we add to ovflist, before 339ddb53d373 we would be woken up by ep_scan_ready_list, and did no wakeup in ep_poll_callback. With that wakeup removed, if we add to ovflist here, we may never wake up. Rather than adding back the ep_scan_ready_list wakeup - which was resulting un uncessary wakeups, trigger a wake-up in ep_poll_callback.
We noticed that one of our workloads was missing wakeups starting with 339ddb53d373 and upon manual inspection, this wakeup seemed missing to me. With this patch added, we no longer see missing wakeups. I haven't yet tried to make a small reproducer, but the existing kselftests in filesystem/epoll passed for me with this patch.
Link: http://lkml.kernel.org/r/20200424025057.118641-1-khazhy@google.com Fixes: 339ddb53d373 ("fs/epoll: remove unnecessary wakeups of nested epoll") Signed-off-by: Khazhismel Kumykov khazhy@google.com Cc: Alexander Viro viro@zeniv.linux.org.uk Cc: Roman Penyaev rpenyaev@suse.de Cc: Heiher r@hev.cc Cc: Jason Baron jbaron@akamai.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---
fs/eventpoll.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
--- a/fs/eventpoll.c~eventpoll-fix-missing-wakeup-for-ovflist-in-ep_poll_callback +++ a/fs/eventpoll.c @@ -1240,7 +1240,7 @@ static int ep_poll_callback(wait_queue_e if (epi->next == EP_UNACTIVE_PTR && chain_epi_lockless(epi)) ep_pm_stay_awake_rcu(epi); - goto out_unlock; + goto out_wakeup_unlock; }
/* If this file is already in the ready list we exit soon */ @@ -1249,6 +1249,7 @@ static int ep_poll_callback(wait_queue_e ep_pm_stay_awake_rcu(epi); }
+out_wakeup_unlock: /* * Wake up ( if active ) both the eventpoll wait list and the ->poll() * wait list. _
Patches currently in -mm which might be from khazhy@google.com are
eventpoll-fix-missing-wakeup-for-ovflist-in-ep_poll_callback.patch