linux-kernel - Re: signalfd API issues (was Re: [PATCH/RFC] signal races/bugs, losing TIF

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Date:	Tue, 5 Jun 2007 21:35:50 -0700 (PDT)
From:	Davide Libenzi <davidel@...ilserver.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
cc:	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Nicholas Miell <nmiell@...cast.net>,
	Linux Kernel list <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Paul Mackerras <paulus@...ba.org>
Subject: Re: signalfd API issues (was Re: [PATCH/RFC] signal races/bugs,
 losing TIF_SIGPENDING and other woes)

On Tue, 5 Jun 2007, Linus Torvalds wrote:

> On Tue, 5 Jun 2007, Davide Libenzi wrote:
> > On Wed, 6 Jun 2007, Benjamin Herrenschmidt wrote:
> > > 
> > > Yeah, synchronous signals should probably never be delivered to another
> > > process, even via signalfd. There's no point delivering a SEGV to
> > > somebody else :-)
> > 
> > That'd be a limitation. Like you can choose to not handle SEGV, you can 
> > choose to have a signalfd listening to it. Of course, not with the 
> > intention to *handle* the signal, but with a notification intent.
> 
> I agree that it would be a limitation, but it would be a sane one.
> 
> How about we try to live with that limitation, if only to avoid the issue 
> of having the private signals being stolen by anybody else. If we actually 
> find a real-live use-case where that is bad in the future, we can re-visit 
> the issue - it's always easier to _expand_ semantics later than it is to 
> restrict them, so I think this thread is a good argument for starting it 
> out in a more restricted form before people start depending on semantics 
> that can be nasty..

Yeah, that's easy. We can exclude them at signalfd creation time.



- Davide


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