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

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Message-ID: <Pine.LNX.4.64.0706051548290.23673@alien.or.mcafeemobile.com>
Date:	Tue, 5 Jun 2007 15:50:57 -0700 (PDT)
From:	Davide Libenzi <davidel@...ilserver.org>
To:	Benjamin Herrenschmidt <benh@...nel.crashing.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 Wed, 6 Jun 2007, Benjamin Herrenschmidt wrote:

> On Tue, 2007-06-05 at 08:52 -0700, Davide Libenzi wrote:
> >         if (tsk == current)
> >                 recalc_sigpending();
> > 
> > What can happen, is that a task may notice TIF_SIGPENDING and not find
> > a 
> > signal once it calls dequeue_signal(), but this is fine as far as
> > signalfd 
> > goes. This should be OK in general, no? 
> 
> 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?



- Davide


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