linux-kernel - Re: [patch 00/11] ANNOUNCE: "Syslets", generic asynchronous system call support

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Message-ID: <Pine.LNX.4.64.0702141756450.7796@alien.or.mcafeemobile.com>
Date:	Wed, 14 Feb 2007 18:07:30 -0800 (PST)
From:	Davide Libenzi <davidel@...ilserver.org>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
cc:	Ingo Molnar <mingo@...e.hu>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Arjan van de Ven <arjan@...radead.org>,
	Christoph Hellwig <hch@...radead.org>,
	Andrew Morton <akpm@....com.au>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Ulrich Drepper <drepper@...hat.com>,
	Zach Brown <zach.brown@...cle.com>,
	Evgeniy Polyakov <johnpol@....mipt.ru>,
	"David S. Miller" <davem@...emloft.net>,
	Benjamin LaHaise <bcrl@...ck.org>,
	Suparna Bhattacharya <suparna@...ibm.com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [patch 00/11] ANNOUNCE: "Syslets", generic asynchronous system
 call support

On Wed, 14 Feb 2007, Jeremy Fitzhardinge wrote:

> Davide Libenzi wrote:
> >> Would this work?
> >>     
> >
> > Hopefully the API will simplify enough so that emulation will becomes 
> > easier.
> >   
> 
> The big question in my mind is how all this stuff interacts with
> signals.  Can a blocked syscall atom be interrupted by a signal?  If so,
> what thread does it get delivered to?  How does sigprocmask affect this
> (is it atomic with respect to blocking atoms)?

Signal context is another thing that we need to transfer to the 
return-to-userspace task, in case we switch. Async threads inherit that 
from the "main" task once they're created, but from there to the 
sys_async_exec syscall, userspace might have changed the signal context, 
and re-emerging with a different one is not an option ;)
We should setup service-threds signal context, so that we can cancel them, 
but the implementation should be hidden to userspace (that will use 
sys_async_cancel - or whatever name -  to do that).



- Davide


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