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From:   Deepa Dinamani <deepa.kernel@gmail.com>
Date:   Tue, 21 May 2019 17:44:19 -0700
Message-ID: <CABeXuvrT-mHomeH-CnuLsWzNCQOfymW01s+HGRaBTNA+u2t28w@mail.gmail.com>
Subject: Re: [PATCH 1/1] signal: Adjust error codes according to restore_user_sigmask()
To:     Eric Wong <e@80x24.org>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Arnd Bergmann <arnd@arndb.de>, dbueso@suse.de, axboe@kernel.dk,
        Davidlohr Bueso <dave@stgolabs.net>,
        Jason Baron <jbaron@akamai.com>,
        Linux FS-devel Mailing List <linux-fsdevel@vger.kernel.org>,
        linux-aio <linux-aio@kvack.org>,
        Omar Kilani <omar.kilani@gmail.com>,
        Thomas Gleixner <tglx@linutronix.de>, stable@vger.kernel.org,
        Oleg Nesterov <oleg@redhat.com>
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On Tue, May 21, 2019 at 5:35 PM Deepa Dinamani <deepa.kernel@gmail.com> wrote:
>
> > > > It's been 2 weeks and this fix hasn't appeared in mmots / mmotm.
> > > > I also noticed it's missing Cc: for stable@ (below)
> > >
> > > Why is a -stable backport needed?  I see some talk above about lost
> > > signals but it is unclear whether these are being observed after fixing
> > > the regression caused by 854a6ed56839a.
> >
> > I guess Deepa's commit messages wasn't clear...
> > I suggest prepending this as the first paragraph to Deepa's
> > original message:
> >
> >   This fixes a bug introduced with 854a6ed56839a which caused
> >   EINTR to not be reported to userspace on epoll_pwait.  Failure
> >   to report EINTR to userspace caused problems with user code
> >   which relies on EINTR to run signal handlers.
>
> This is not what the patch fixed.
>
> The notable change is userspace is that now whenever a signal is
> delivered, the return value is adjusted to reflect the signal
> delivery.
> Prior to this patch, there was a window, however small it might have
> been, when the signal was delivered but the errono was not adjusted
> appropriately.
> This is because of the regression caused by 854a6ed56839a, which
> extended the window of delivery of signals that was delivered to
> userspace.
> The patch also fixes more than sys_epoll_pwait().
>
> I will post a follow up patch.
>
> >
> > > IOW, can we please have a changelog which has a clear and complete
> > > description of the user-visible effects of the change.
> > >
> > > And please Cc Oleg.
>
> I will cc Oleg.

Also the commit message was brief because the issue was explained in
the link that was quoted in the commit message.

Detailed issue discussion permalink:
https://lore.kernel.org/linux-fsdevel/20190427093319.sgicqik2oqkez3wk@dcvr/

-Deepa