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Date: Thu, 13 Feb 2014 19:10:13 +0100
From: Oleg Nesterov <oleg@redhat.com>
Subject: Re: 3.14-rc2 XFS backtrace because irqs_disabled.
Message-ID: <20140213181013.GA15596@redhat.com>
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To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Eric Sandeen <sandeen@sandeen.net>, Linux Kernel <linux-kernel@vger.kernel.org>, xfs@oss.sgi.com, Al Viro <viro@zeniv.linux.org.uk>, Dave Jones <davej@redhat.com>

On 02/13, Linus Torvalds wrote:
>
> On Thu, Feb 13, 2014 at 9:40 AM, Oleg Nesterov <oleg@redhat.com> wrote:
> >
> > And we should be careful with SIGQUEUE_PREALLOC, at least
> > collect_signal() should not do list_del_init()... Plus we need to
> > handle the SEND_SIG_FORCED-like case.
>
> I don't think the users need to care. They'd just call
> "sigqueue_free()" not knowing about our preallocations etc.

Yes, but we need to be careful to avoid the races with
release_posix_timer().

> That kind
> of detail should be confined to inside signal.c.

Yes, sure.

> But there really aren't that many users. There's a couple of
> "dequeue_signal_lock()" users, but they don't actually *want* the
> siginfo at all (they're kernel threads), so we can just make that
> function free the siginfo immediately (and get rid of the totally
> unnecessay kernel stack allocation).

Yes. Perhaps this helper should be changed/renamed. And perhaps we
can even change __send_signal() to avoid __sigqueue_alloc() if
PF_KTHREAD. Or sig == SIGKILL.

Oleg.

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