linux-kernel - Re: [PATCH 1/3] comm: Introduce comm_lock seqlock to protect task->comm access

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Message-ID: <1305596867.2915.109.camel@work-vm>
Date:	Mon, 16 May 2011 18:47:47 -0700
From:	John Stultz <john.stultz@...aro.org>
To:	Jiri Slaby <jirislaby@...il.com>
Cc:	LKML <linux-kernel@...r.kernel.org>, "Ted Ts'o" <tytso@....edu>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	David Rientjes <rientjes@...gle.com>,
	Dave Hansen <dave@...ux.vnet.ibm.com>,
	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org
Subject: Re: [PATCH 1/3] comm: Introduce comm_lock seqlock to protect
 task->comm access

On Tue, 2011-05-17 at 00:01 +0200, Jiri Slaby wrote:
> On 05/16/2011 11:19 PM, John Stultz wrote:
> > diff --git a/include/linux/init_task.h b/include/linux/init_task.h
> > index caa151f..b69d94b 100644
> > --- a/include/linux/init_task.h
> > +++ b/include/linux/init_task.h
> > @@ -161,6 +161,7 @@ extern struct cred init_cred;
> >  	.group_leader	= &tsk,						\
> >  	RCU_INIT_POINTER(.real_cred, &init_cred),			\
> >  	RCU_INIT_POINTER(.cred, &init_cred),				\
> > +	.comm_lock	= __SPIN_LOCK_UNLOCKED(tsk.comm_lock),		\
> 
> Hmm, you should also init the spinlock somewhere in copy_process.
> Otherwise when a process is forked in the middle of [gs]et_task_comm
> called on it on another cpu, you have two locked locks and only the
> parent's will be unlocked, right?

Ah, yep. Fixed for the next version.

thanks!
-john

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