linux-kernel - Re: [Devel] Re: [PATCH 08/10] Introduce functions to restart a process

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Message-Id: <1224669979.4210.15.camel@localhost.localdomain>
Date:	Wed, 22 Oct 2008 12:06:19 +0200
From:	Greg Kurz <gkurz@...ibm.com>
To:	Louis.Rilling@...labs.com
Cc:	Andrey Mirkin <major@...nvz.org>,
	containers@...ts.linux-foundation.org,
	Cedric Le Goater <clg@...ibm.com>,
	linux-kernel@...r.kernel.org, Pavel Emelyanov <xemul@...nvz.org>
Subject: Re: [Devel] Re: [PATCH 08/10] Introduce functions to restart a
	process

On Wed, 2008-10-22 at 11:25 +0200, Louis Rilling wrote:
> Do you checkpoint uninterruptible syscalls as well? If only interruptible
> syscalls are checkpointed, I'd say that either this syscall uses ERESTARTSYS or
> ERESTART_RESTARTBLOCK, and then signal handling code already does the trick, or
> this syscall does not restart itself when interrupted, and well, this is life,
> userspace just sees -EINTR, which is allowed by the syscall spec.
> Actually this is how we checkpoint/migrate tasks in interruptible syscalls in
> Kerrighed and this works.
> 
> Louis
> 

I don't know Kerrighed internals but I understand you perform checkpoint
with a signal handler. Right ? This approach has a huge benefit: the
signal handling code do all the arch dependant stuff to save registers
in user memory.

-- 
Gregory Kurz                                     gkurz@...ibm.com
Software Engineer @ IBM/Meiosys                  http://www.ibm.com
Tel +33 (0)534 638 479                           Fax +33 (0)561 400 420

"Anarchy is about taking complete responsibility for yourself."
        Alan Moore.

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