From: Andrew Morton <akpm@linux-foundation.org>
To: Khazhismel Kumykov <khazhy@google.com>
Cc: viro@zeniv.linux.org.uk, rpenyaev@suse.de, r@hev.cc,
linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
Jason Baron <jbaron@akamai.com>
Subject: Re: [PATCH] eventpoll: fix missing wakeup for ovflist in ep_poll_callback
Date: Thu, 23 Apr 2020 20:31:59 -0700 [thread overview]
Message-ID: <20200423203159.c9fc9988649e08d59e13e64d@linux-foundation.org> (raw)
In-Reply-To: <20200424025057.118641-1-khazhy@google.com>
On Thu, 23 Apr 2020 19:50:57 -0700 Khazhismel Kumykov <khazhy@google.com> wrote:
> 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.
I'm no longer familiar with this code, so I'll await input from others.
> Fixes: 339ddb53d373 ("fs/epoll: remove unnecessary wakeups of nested epoll")
> Signed-off-by: Khazhismel Kumykov <khazhy@google.com>
However it sounds like a cc:stable would be warranted here, so that
earlier affected kernels get the fix?
next prev parent reply other threads:[~2020-04-24 3:32 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-24 2:50 [PATCH] eventpoll: fix missing wakeup for ovflist in ep_poll_callback Khazhismel Kumykov
2020-04-24 3:31 ` Andrew Morton [this message]
2020-04-24 10:11 ` Roman Penyaev
2020-04-24 18:50 ` Khazhismel Kumykov
2020-04-24 19:00 ` [PATCH v2] " Khazhismel Kumykov
2020-04-25 16:17 ` Jason Baron
2020-04-25 20:59 ` Khazhismel Kumykov
2020-04-27 20:38 ` Jason Baron
2020-04-28 18:10 ` Roman Penyaev
2020-04-29 4:12 ` Jason Baron
2020-04-29 14:38 ` Roman Penyaev
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