From: Mikulas Patocka <mpatocka@redhat.com>
To: NeilBrown <neilb@suse.com>
Cc: Shaohua Li <shli@kernel.org>,
linux-raid@vger.kernel.org, linux-kernel@vger.kernel.org,
Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH] md: don't use flush_signals in userspace processes
Date: Thu, 8 Jun 2017 18:52:50 -0400 (EDT) [thread overview]
Message-ID: <alpine.LRH.2.02.1706081847150.3603@file01.intranet.prod.int.rdu2.redhat.com> (raw)
In-Reply-To: <87h8zrart4.fsf@notabene.neil.brown.name>
On Thu, 8 Jun 2017, NeilBrown wrote:
> On Wed, Jun 07 2017, Mikulas Patocka wrote:
>
> > The function flush_signals clears all pending signals for the process. It
> > may be used by kernel threads when we need to prepare a kernel thread for
> > responding to signals. However using this function for an userspaces
> > processes is incorrect - clearing signals without the program expecting it
> > can cause misbehavior.
> >
> > The raid1 and raid5 code uses flush_signals in its request routine because
> > it wants to prepare for an interruptible wait. This patch drops
> > flush_signals and uses sigprocmask instead to block all signals (including
> > SIGKILL) around the schedule() call. The signals are not lost, but the
> > schedule() call won't respond to them.
> >
> > Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
> > Cc: stable@vger.kernel.org
>
> Thanks for catching that!
>
> Acked-by: NeilBrown <neilb@suse.com>
>
> NeilBrown
BTW. why does md_thread do "allow_signal(SIGKILL)" and then
"if (signal_pending(current)) flush_signals(current)"?
Does userspace really send SIGKILL to MD kernel threads? The SIGKILL will
be lost when flush_signals is called, so it looks quite dubious.
Mikulas
next prev parent reply other threads:[~2017-06-08 22:52 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-06-07 23:05 [PATCH] md: don't use flush_signals in userspace processes Mikulas Patocka
2017-06-08 6:59 ` NeilBrown
[not found] ` <20170608171551.ytxk3yz6xxsfbqma@kernel.org>
2017-06-08 20:51 ` Mikulas Patocka
2017-06-08 21:24 ` NeilBrown
2017-06-08 22:58 ` Shaohua Li
2017-06-09 1:49 ` NeilBrown
2017-06-08 22:52 ` Mikulas Patocka [this message]
2017-06-09 1:55 ` NeilBrown
2017-06-09 3:27 ` Henrique de Moraes Holschuh
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