linux-kernel - Re: 3.14-rc2 XFS backtrace because irqs

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Date:	Sat, 15 Feb 2014 15:22:51 +0000
From:	Al Viro <viro@...IV.linux.org.uk>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Dave Chinner <david@...morbit.com>,
	Dave Jones <davej@...hat.com>,
	Eric Sandeen <sandeen@...deen.net>,
	Linux Kernel <linux-kernel@...r.kernel.org>, xfs@....sgi.com
Subject: Re: 3.14-rc2 XFS backtrace because irqs_disabled.

On Sat, Feb 15, 2014 at 03:27:00PM +0100, Oleg Nesterov wrote:

> 1. info->q can be already freed if SIGQUEUE_PREALLOC.
> 
>    Once get_signal_to_deliver() or any other caller drops ->siglock
>    another thread can do sys_timer_delete()->sigqueue_free().

How the devil would it find the sucker?  It's off the list already.

> 2. We need to move do_schedule_next_timer() from dequeue_signal()
>    here.
> 
>    Otherwise ->q can be reused/overwritten by the next send_sigqueue()
>    right affter ->siglock is dropped.

Ditto.  We rip them out of queue on collect_signal(); the only thing we do
not do is actual __sigqueue_free().
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