From: Oleg Nesterov <oleg@redhat.com>
To: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org,
Russell King <linux@arm.linux.org.uk>, Tejun Heo <tj@kernel.org>,
Arnd Bergmann <arnd@arndb.de>,
Roland McGrath <roland@hack.frob.com>
Subject: Re: [RFC] TIF_NOTIFY_RESUME, arch/*/*/*signal*.c and all such
Date: Wed, 25 Apr 2012 15:03:29 +0200 [thread overview]
Message-ID: <20120425130329.GA16413@redhat.com> (raw)
In-Reply-To: <20120425125042.GF6871@ZenIV.linux.org.uk>
On 04/25, Al Viro wrote:
>
> On Wed, Apr 25, 2012 at 02:37:46PM +0200, Oleg Nesterov wrote:
> > As for sys_sigsuspend() and this race in particular:
> >
> > > Arrival of a signal that has userland handler
> > > and that isn't blocked by the mask given to sigsuspend() should terminate
> > > sigsuspend().
> >
> > Yes. But note that do_signal() restores the old sigmask. This means that
> > the signal we get after the first do_signal() was not blocked before
> > sigsuspend() was called. So, to some extent, we can pretend that the
> > handler was executed before sigsuspend() and it was never restarted.
>
> Signal might have already arrived by the time we restore sigmask.
Yes, and it sets TIF_SIGPENDING, but unless I missed something this doesn't
matter.
> So no,
> it might have been blocked prior to sigsuspend().
If it was not blocked, then the next do_signal()->get_signal_to_deliver()
returns 0 and clears TIF_SIGPENDING. After that we finally re-enter
sys_sigsuspend() and (assuming it unblocks this sig) notice this pending
signal again and return -EINTR eventually.
Oleg.
next prev parent reply other threads:[~2012-04-25 13:04 UTC|newest]
Thread overview: 68+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20120420004303.GB6871@ZenIV.linux.org.uk>
[not found] ` <CA+55aFxQR8g3TycW7nOVjjnnsaWWW-Gh74-bV6rUm+7SRTm25g@mail.gmail.com>
[not found] ` <20120420025438.GD6871@ZenIV.linux.org.uk>
[not found] ` <CA+55aFzinX_6DVvDTyxrsP6VEHVY2Q+Y=e+qksnAjR+oT3GZew@mail.gmail.com>
[not found] ` <20120420080914.GF6871@ZenIV.linux.org.uk>
[not found] ` <CA+55aFxia+u3VAf0qN-2wv7DyAQZK-Z8=n=cqUvo--+C905aFg@mail.gmail.com>
[not found] ` <20120420160848.GG6871@ZenIV.linux.org.uk>
[not found] ` <20120420164239.GH6871@ZenIV.linux.org.uk>
[not found] ` <CA+55aFzuTspDyyLaOA-g-dTWydaUeeWo9uVGR+rZ=ZJzPW_Ocw@mail.gmail.com>
[not found] ` <20120420180748.GI6871@ZenIV.linux.org.uk>
2012-04-23 18:01 ` [RFC] TIF_NOTIFY_RESUME, arch/*/*/*signal*.c and all such Al Viro
2012-04-23 18:01 ` Al Viro
2012-04-23 18:37 ` Oleg Nesterov
2012-04-24 7:26 ` Al Viro
2012-04-25 3:06 ` Al Viro
2012-04-25 3:06 ` Al Viro
2012-04-25 12:37 ` Oleg Nesterov
2012-04-25 12:50 ` Al Viro
2012-04-25 13:03 ` Oleg Nesterov [this message]
2012-04-25 13:32 ` Oleg Nesterov
2012-04-25 13:32 ` Al Viro
2012-04-25 14:52 ` Oleg Nesterov
2012-04-25 15:46 ` Oleg Nesterov
2012-04-25 16:10 ` Al Viro
2012-04-25 17:02 ` Oleg Nesterov
2012-04-25 17:51 ` Al Viro
2012-04-26 7:15 ` Martin Schwidefsky
2012-04-26 7:25 ` David Miller
2012-04-26 13:52 ` Oleg Nesterov
2012-04-26 14:31 ` Martin Schwidefsky
2012-04-26 14:31 ` Martin Schwidefsky
2012-04-26 13:22 ` Oleg Nesterov
2012-04-26 18:37 ` Oleg Nesterov
2012-04-26 23:19 ` Al Viro
2012-04-27 17:24 ` Oleg Nesterov
2012-04-27 17:24 ` Oleg Nesterov
2012-04-27 17:54 ` Oleg Nesterov
2012-05-02 10:37 ` Matt Fleming
2012-05-02 14:14 ` Al Viro
2012-05-02 14:14 ` Al Viro
2012-04-27 18:45 ` Al Viro
2012-04-27 19:14 ` Geert Uytterhoeven
2012-04-27 19:34 ` Al Viro
2012-04-29 22:51 ` Al Viro
2012-04-30 6:39 ` Greg Ungerer
2012-04-27 19:42 ` Al Viro
2012-04-27 20:20 ` Roland McGrath
2012-04-27 21:12 ` Al Viro
2012-04-27 21:27 ` Roland McGrath
2012-04-27 23:15 ` Al Viro
2012-04-27 23:32 ` Al Viro
2012-04-29 4:12 ` Al Viro
2012-04-29 4:12 ` Al Viro
2012-04-30 8:06 ` Martin Schwidefsky
2012-04-27 23:50 ` Al Viro
2012-04-28 18:51 ` [PATCH] arch/tile: avoid calling do_signal() after fork from a kernel thread Chris Metcalf
2012-04-28 20:55 ` Al Viro
2012-04-28 20:55 ` Al Viro
2012-04-28 21:46 ` Chris Metcalf
2012-04-29 0:55 ` Al Viro
2012-04-28 18:51 ` [PATCH v2] arch/tile: fix up some issues in calling do_work_pending() Chris Metcalf
2012-04-29 3:49 ` [PATCH] arch/tile: avoid calling do_signal() after fork from a kernel thread Chris Metcalf
2012-04-29 3:49 ` Chris Metcalf
2012-04-28 2:42 ` [RFC] TIF_NOTIFY_RESUME, arch/*/*/*signal*.c and all such Al Viro
2012-04-28 3:32 ` Al Viro
2012-04-28 3:36 ` Al Viro
2012-04-29 16:33 ` Oleg Nesterov
2012-04-29 16:18 ` Oleg Nesterov
2012-04-29 18:05 ` Al Viro
2012-05-01 4:31 ` Al Viro
2012-05-01 5:06 ` Mike Frysinger
2012-05-01 5:52 ` Al Viro
2012-05-02 17:24 ` Al Viro
2012-05-02 18:30 ` Oleg Nesterov
2012-04-29 16:41 ` Oleg Nesterov
2012-04-29 16:41 ` Oleg Nesterov
2012-04-29 18:09 ` Al Viro
2012-04-29 18:25 ` Oleg Nesterov
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