linux-kernel - Re: [PATCH/RFC] signal races/bugs, losing TIF

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Message-Id: <1181084368.31677.149.camel@localhost.localdomain>
Date:	Wed, 06 Jun 2007 08:59:28 +1000
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	Davide Libenzi <davidel@...ilserver.org>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Linux Kernel list <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Paul Mackerras <paulus@...ba.org>
Subject: Re: [PATCH/RFC] signal races/bugs, losing TIF_SIGPENDING and other
	woes

On Tue, 2007-06-05 at 15:50 -0700, Davide Libenzi wrote:
> > What about the code in __dequeue_signal though ? That notifier thing
> is
> > used by the DRI though I'm not sure what would happen if it acts on
> the
> > wrong task.
> 
> Hmm, looking at the comments in block_all_signals(), it seems that
> they're 
> interested in the fact that a specific task dequeue the signal. So,
> at 
> a first sight, it seems that such code should not not be executed if 
> another task dequeue the message. What do you think?

Yes, I think the idea is that the DRM uses that to prevent signals to be
delivered to the task that is blocking them with the notifier (I have no
idea why they can't use the normal block mecanism for that... looks like
a hack to me).

So I suppose it's fine, as long as you add a test of tsk == current to
avoid calling it.

Ben.


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