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

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From: John Stultz <john.stultz@linaro.org>
To: Jiri Slaby <jirislaby@gmail.com>
Cc: LKML <linux-kernel@vger.kernel.org>, "Ted Ts'o" <tytso@mit.edu>,
	KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
	David Rientjes <rientjes@google.com>,
	Dave Hansen <dave@linux.vnet.ibm.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	linux-mm@kvack.org
Subject: Re: [PATCH 1/3] comm: Introduce comm_lock seqlock to protect task->comm access
Date: Mon, 16 May 2011 18:47:47 -0700	[thread overview]
Message-ID: <1305596867.2915.109.camel@work-vm> (raw)
In-Reply-To: <4DD19EB5.7060900@gmail.com>

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

WARNING: multiple messages have this Message-ID (diff)

From: John Stultz <john.stultz@linaro.org>
To: Jiri Slaby <jirislaby@gmail.com>
Cc: LKML <linux-kernel@vger.kernel.org>, Ted Ts'o <tytso@mit.edu>,
	KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
	David Rientjes <rientjes@google.com>,
	Dave Hansen <dave@linux.vnet.ibm.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	linux-mm@kvack.org
Subject: Re: [PATCH 1/3] comm: Introduce comm_lock seqlock to protect task->comm access
Date: Mon, 16 May 2011 18:47:47 -0700	[thread overview]
Message-ID: <1305596867.2915.109.camel@work-vm> (raw)
In-Reply-To: <4DD19EB5.7060900@gmail.com>

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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next prev parent reply	other threads:[~2011-05-17  1:47 UTC|newest]

Thread overview: 58+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-05-16 21:19 [PATCH 0/3] v4 Improve task->comm locking situation John Stultz
2011-05-16 21:19 ` John Stultz
2011-05-16 21:19 ` [PATCH 1/3] comm: Introduce comm_lock seqlock to protect task->comm access John Stultz
2011-05-16 21:19   ` John Stultz
2011-05-16 22:01   ` Jiri Slaby
2011-05-16 22:01     ` Jiri Slaby
2011-05-17  1:47     ` John Stultz [this message]
2011-05-17  1:47       ` John Stultz
2011-05-18  0:28   ` KOSAKI Motohiro
2011-05-18  0:28     ` KOSAKI Motohiro
2011-05-16 21:19 ` [PATCH 2/3] printk: Add %ptc to safely print a task's comm John Stultz
2011-05-16 21:19   ` John Stultz
2011-05-16 21:54   ` Jiri Slaby
2011-05-16 21:54     ` Jiri Slaby
2011-05-16 23:10     ` John Stultz
2011-05-16 23:10       ` John Stultz
2011-05-16 23:56       ` Joe Perches
2011-05-16 23:56         ` Joe Perches
2011-05-17  0:11         ` John Stultz
2011-05-17  0:11           ` John Stultz
2011-05-17  7:21         ` Jiri Slaby
2011-05-17  7:21           ` Jiri Slaby
2011-05-18  0:32   ` KOSAKI Motohiro
2011-05-18  0:32     ` KOSAKI Motohiro
2011-05-16 21:19 ` [PATCH 3/3] checkpatch.pl: Add check for task comm references John Stultz
2011-05-16 21:19   ` John Stultz
2011-05-16 21:29   ` Michal Nazarewicz
2011-05-16 21:29     ` Michal Nazarewicz
2011-05-16 21:34     ` David Rientjes
2011-05-16 21:34       ` David Rientjes
2011-05-16 23:04       ` Joe Perches
2011-05-16 23:04         ` Joe Perches
2011-05-16 23:11         ` Michal Nazarewicz
2011-05-16 23:11           ` Michal Nazarewicz
2011-05-16 23:22           ` Joe Perches
2011-05-16 23:22             ` Joe Perches
2011-05-18  3:16 ` [PATCH 0/3] v4 Improve task->comm locking situation Tetsuo Handa
2011-05-18  4:10   ` KOSAKI Motohiro
2011-05-18  4:15   ` John Stultz
2011-05-18  5:27     ` Tetsuo Handa
  -- strict thread matches above, loose matches on Subject: below --
2011-05-12 23:02 [PATCH 0/3] v3 " John Stultz
2011-05-12 23:02 ` [PATCH 1/3] comm: Introduce comm_lock seqlock to protect task->comm access John Stultz
2011-05-12 23:02   ` John Stultz
2011-05-13 11:13   ` KOSAKI Motohiro
2011-05-13 11:13     ` KOSAKI Motohiro
2011-05-13 18:27     ` John Stultz
2011-05-13 18:27       ` John Stultz
2011-05-14 11:12       ` KOSAKI Motohiro
2011-05-14 11:12         ` KOSAKI Motohiro
2011-05-16 20:34         ` John Stultz
2011-05-16 20:34           ` John Stultz
2011-05-11  0:23 [RFC][PATCH 0/3] v2 Improve task->comm locking situation John Stultz
2011-05-11  0:23 ` [PATCH 1/3] comm: Introduce comm_lock seqlock to protect task->comm access John Stultz
2011-05-11  0:23   ` John Stultz
2011-05-11 17:39   ` Andi Kleen
2011-05-11 17:39     ` Andi Kleen
2011-05-12 22:00   ` David Rientjes
2011-05-12 22:00     ` David Rientjes
2011-04-28  4:03 [RFC][PATCH 0/3] Improve task->comm locking situation John Stultz
2011-04-28  4:03 ` [PATCH 1/3] comm: Introduce comm_lock seqlock to protect task->comm access John Stultz
2011-04-28  4:03   ` John Stultz

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