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Re: 3.14-rc2 XFS backtrace because irqs_disabled.

To: Al Viro <viro@xxxxxxxxxxxxxxxxxx>, Oleg Nesterov <oleg@xxxxxxxxxx>
Subject: Re: 3.14-rc2 XFS backtrace because irqs_disabled.
From: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Date: Wed, 12 Feb 2014 13:32:55 -0800
Cc: Dave Chinner <david@xxxxxxxxxxxxx>, Dave Jones <davej@xxxxxxxxxx>, Eric Sandeen <sandeen@xxxxxxxxxxx>, Linux Kernel <linux-kernel@xxxxxxxxxxxxxxx>, xfs@xxxxxxxxxxx
Delivered-to: xfs@xxxxxxxxxxx
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On Wed, Feb 12, 2014 at 1:14 PM, Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote:
>
> Umm...  What if we delay __sigqueue_free()?  After all, that's where the
> fat sucker normally comes from.  That way we might get away with much
> smaller structure on stack...

Sounds like the RightThing(tm) to do to me, and I don't see why it
wouldn't work.

We'd have to teach each user of "dequeue_signal()" to free the siginfo
thing. Which shouldn't be too bad - I think we've collected all of
that into generic code, and there isn't the mass or architecture code
that knows about these things any more. But there are a few odd
drivers etc and signalfd. I didn't look at what the lifetimes were.

Adding Oleg to the cc, since any time we touch any of that code, he
should be involved. Oleg - the issue is the biggish size of 'struct
ksignal' on stack, brought on by the silly "put a whole siginfo_t in
it".

            Linus

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