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

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Message-ID: <CA+55aFwoWT-0A_KTkXMkNqOy8hc=YmouTMBgWUD_z+8qYPphjA@mail.gmail.com>
Date:	Tue, 11 Feb 2014 18:52:19 -0800
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Al Viro <viro@...iv.linux.org.uk>
Cc:	Dave Jones <davej@...hat.com>, Eric Sandeen <sandeen@...deen.net>,
	Dave Chinner <david@...morbit.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>, xfs@....sgi.com
Subject: Re: 3.14-rc2 XFS backtrace because irqs_disabled.

On Tue, Feb 11, 2014 at 5:09 PM, Al Viro <viro@...iv.linux.org.uk> wrote:
>
> Slap the check in vfs_create(), see if interrupts had been disabled by it or
> by something in ->create().  Since it's reproducible...

path_openat() starts off with a get_empty_filp(), which allocates a
file pointer with GFP_KERNEL. So that should have triggered the
might_sleep warning if irq's were already disabled at that point.

So it's not before that - in particular, it's not in the signal
handling or do_coredump() paths.

Also, at least xfs_buf_lock() - which is much deeper in that chain -
does a down(&bp->b_sema). I'm disguested that that doesn't have a
might_sleep() in it.

Dave, mind adding a "might_sleep()" to the top of
"down[_interruptible]()". It's silly to not have coverage of semaphore
use in bad contexts.

             Linus
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