linux-kernel - Re: [PATCH vfs/vfs.fixes v2] eventpoll: Set epoll timeout if it's in the future

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Message-ID: <zvkvenkysbzves2qzknju5pmaws322r3lugzbstv6kuxcbw23k@mtddhwfxj3ce>
Date: Tue, 29 Apr 2025 12:19:15 +0200
From: Jan Kara <jack@...e.cz>
To: Joe Damato <jdamato@...tly.com>
Cc: Carlos Llamas <cmllamas@...gle.com>, Jan Kara <jack@...e.cz>, 
	Christian Brauner <brauner@...nel.org>, linux-fsdevel@...r.kernel.org, 
	Alexander Viro <viro@...iv.linux.org.uk>, "David S. Miller" <davem@...emloft.net>, 
	Eric Dumazet <edumazet@...gle.com>, Sridhar Samudrala <sridhar.samudrala@...el.com>, 
	Alexander Duyck <alexander.h.duyck@...el.com>, open list <linux-kernel@...r.kernel.org>, 
	Tudor Ambarus <tudor.ambarus@...aro.org>, William McVicker <willmcvicker@...gle.com>
Subject: Re: [PATCH vfs/vfs.fixes v2] eventpoll: Set epoll timeout if it's in
 the future

On Mon 28-04-25 15:41:17, Joe Damato wrote:
> On Mon, Apr 28, 2025 at 10:32:31PM +0000, Carlos Llamas wrote:
> > On Mon, Apr 28, 2025 at 09:50:02AM -0700, Joe Damato wrote:
> > > Thank you for spotting that and sorry for the trouble.
> > 
> > This was also flagged by our Android's epoll_pwait2 tests here:
> > https://android.googlesource.com/platform/bionic/+/refs/heads/main/tests/sys_epoll_test.cpp
> > They would all timeout, so the hang reported by Christian fits.
> > 
> > 
> > > Christian / Jan what would be the correct way for me to deal with
> > > this? Would it be to post a v3 (re-submitting the patch in its
> > > entirety) or to post a new patch that fixes the original and lists
> > > the commit sha from vfs.fixes with a Fixes tag ?
> > 
> > The original commit has landed in mainline already, so it needs to be
> > new patch at this point. If if helps, here is the tag:
> > Fixes: 0a65bc27bd64 ("eventpoll: Set epoll timeout if it's in the future")
> > 
> > > diff --git a/fs/eventpoll.c b/fs/eventpoll.c
> > > index 4bc264b854c4..1a5d1147f082 100644
> > > --- a/fs/eventpoll.c
> > > +++ b/fs/eventpoll.c
> > > @@ -2111,7 +2111,9 @@ static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events,
> > > 
> > >                 write_unlock_irq(&ep->lock);
> > > 
> > > -               if (!eavail && ep_schedule_timeout(to))
> > > +               if (!ep_schedule_timeout(to))
> > > +                       timed_out = 1;
> > > +               else if (!eavail)
> > >                         timed_out = !schedule_hrtimeout_range(to, slack,
> > >                                                               HRTIMER_MODE_ABS);
> > >                 __set_current_state(TASK_RUNNING);
> > 
> > I've ran your change through our internal CI and I confirm it fixes the
> > hangs seen on our end. If you send the fix feel free to add:
> > 
> > Tested-by: Carlos Llamas <cmllamas@...gle.com>
> 
> Thanks, will do.
> 
> I was waiting to hear back from Christian / Jan if they are OK with
> the proposed fix before submitting something, but glad to hear it
> fixes the issue for you. Sorry for the trouble.

Yep, a new patch submission with proper Fixes tag is needed at this point.

								Honza
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR