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From: Oleg Nesterov <oleg@tv-sign.ru>
To: Cedric Le Goater <clg@fr.ibm.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Andrew Morton <akpm@osdl.org>,
	containers@lists.osdl.org
Subject: Re: [patch -mm] update mq_notify to use a struct pid
Date: Mon, 11 Sep 2006 19:48:33 +0400	[thread overview]
Message-ID: <20060911154833.GB82@oleg> (raw)
In-Reply-To: <450537B6.1020509@fr.ibm.com>

On 09/11, Cedric Le Goater wrote:
>
> Eric W. Biederman wrote:
> > Cedric Le Goater <clg@fr.ibm.com> writes:
> > 
> >> message queues can signal a process waiting for a message.
> >>
> >> this patch replaces the pid_t value with a struct pid to avoid pid wrap
> >> around problems.
> >>
> >> Signed-off-by: Cedric Le Goater <clg@fr.ibm.com>
> >> Cc: Eric Biederman <ebiederm@xmission.com>
> >> Cc: Andrew Morton <akpm@osdl.org>
> >> Cc: containers@lists.osdl.org
> > 
> > Signed-off-by: Eric Biederman <ebiederm@xmission.com>
> > 
> > I was just about to send out this patch in a couple more hours.
> 
> Well, you did the same with the usb/devio.c and friends :)
> 
> > So expect the fact we wrote the same code is a good sign :)
> 
> How does oleg feel about it ? I've seen some long thread on possible race
> conditions with put_pid() and solutions with rcu. I didn't quite get all of
> it ... it will need another run for me.

I assume you are talking about this patch:
	http://marc.theaimsgroup.com/?l=linux-mm-commits&m=115773820415171

I think it's ok, info->notify_owner is always used under info->lock.

This is simple. If, for example, mqueue_read_file() didn't take info->lock,
then we have a problem: pid_nr() may read a freed memory in case when
__do_notify()->put_pid() happens at the same time.

In this context info->notify_owner is a usual refcounted object, no special
attention is needed.

Oleg.


      parent reply	other threads:[~2006-09-11 15:48 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2006-09-08 16:39 Cedric Le Goater
2006-09-09  2:39 ` Eric W. Biederman
2006-09-11 10:17   ` Cedric Le Goater
2006-09-11 11:09     ` Eric W. Biederman
2006-09-11 14:05       ` Cedric Le Goater
2006-09-11 19:01         ` Eric W. Biederman
2006-09-11 21:53           ` Cedric Le Goater
2006-09-12  1:22             ` Eric W. Biederman
2006-09-12 15:37               ` Cedric Le Goater
2006-09-12 16:03                 ` Eric W. Biederman
2006-09-12 11:05           ` Herbert Poetzl
2006-09-12 15:14             ` Eric W. Biederman
2006-09-14 20:01             ` [PATCH/RFC] kthread API conversion for dvb_frontend and av7110 Herbert Poetzl
2006-09-14 21:07               ` Cedric Le Goater
2006-09-14 22:10                 ` Herbert Poetzl
2006-11-17  1:50                   ` Andrew de Quincey
2006-11-22 14:56                     ` [Devel] " Cedric Le Goater
2006-11-22 21:32                       ` [v4l-dvb-maintainer] " Andrew de Quincey
2007-01-24 15:47                       ` Cedric Le Goater
2006-12-12 22:58                     ` Eric W. Biederman
2006-12-12 23:13                       ` Herbert Poetzl
2006-12-13 15:55                         ` [Devel] " Cedric Le Goater
2006-09-11 15:48     ` Oleg Nesterov [this message]

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