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

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Message-Id: <1181028453.31677.127.camel@localhost.localdomain>
Date:	Tue, 05 Jun 2007 17:27:33 +1000
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	Nicholas Miell <nmiell@...cast.net>
Cc:	Davide Libenzi <davidel@...ilserver.org>,
	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 Mon, 2007-06-04 at 23:09 -0700, Nicholas Miell wrote:
> signalfd() doesn't deliver thread-targeted signals to the wrong
> threads,
> does it?
> 
> Hmm.
> 
> It looks like reading from a signalfd will give you either
> process-global signals or the thread-specific signals that are
> targeted
> towards the thread that originally created the signalfd (regardless of
> which thread actually calls read()).
> 
> Which is weird, to say the least. Definitely needs to be noted in the
> man page, which doesn't seem to exist yet.
> 
> Is there a reason why signalfd() doesn't behave like regular signals
> in
> this regard? 

It's worse than that ... by being able to call dequeue_signal from the
contxt of another thread than the one dequeuing from.

Ben.


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