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From: John Stultz <john.stultz@linaro.org>
To: Andi Kleen <andi@firstfloor.org>
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 2/3] printk: Add %ptc to safely print a task's comm
Date: Wed, 11 May 2011 14:04:27 -0700	[thread overview]
Message-ID: <1305147867.2883.2.camel@work-vm> (raw)
In-Reply-To: <m2sjsli1ft.fsf@firstfloor.org>

On Wed, 2011-05-11 at 10:36 -0700, Andi Kleen wrote:
> John Stultz <john.stultz@linaro.org> writes:
> 
> > Acessing task->comm requires proper locking. However in the past
> > access to current->comm could be done without locking. This
> > is no longer the case, so all comm access needs to be done
> > while holding the comm_lock.
> >
> > In my attempt to clean up unprotected comm access, I've noticed
> > most comm access is done for printk output. To simpify correct
> > locking in these cases, I've introduced a new %ptc format,
> > which will safely print the corresponding task's comm.
> >
> > Example use:
> > printk("%ptc: unaligned epc - sending SIGBUS.\n", current);
> 
> Neat. But you probably want a checkpatch rule for this too
> to catch new offenders.

Yea. That's on my queue.

thanks
-john



WARNING: multiple messages have this Message-ID (diff)
From: John Stultz <john.stultz@linaro.org>
To: Andi Kleen <andi@firstfloor.org>
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 2/3] printk: Add %ptc to safely print a task's comm
Date: Wed, 11 May 2011 14:04:27 -0700	[thread overview]
Message-ID: <1305147867.2883.2.camel@work-vm> (raw)
In-Reply-To: <m2sjsli1ft.fsf@firstfloor.org>

On Wed, 2011-05-11 at 10:36 -0700, Andi Kleen wrote:
> John Stultz <john.stultz@linaro.org> writes:
> 
> > Acessing task->comm requires proper locking. However in the past
> > access to current->comm could be done without locking. This
> > is no longer the case, so all comm access needs to be done
> > while holding the comm_lock.
> >
> > In my attempt to clean up unprotected comm access, I've noticed
> > most comm access is done for printk output. To simpify correct
> > locking in these cases, I've introduced a new %ptc format,
> > which will safely print the corresponding task's comm.
> >
> > Example use:
> > printk("%ptc: unaligned epc - sending SIGBUS.\n", current);
> 
> Neat. But you probably want a checkpatch rule for this too
> to catch new offenders.

Yea. That's on my queue.

thanks
-john


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  reply	other threads:[~2011-05-11 21:04 UTC|newest]

Thread overview: 76+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-05-11  0:23 [RFC][PATCH 0/3] v2 Improve task->comm locking situation John Stultz
2011-05-11  0:23 ` 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
2011-05-11  0:23 ` [PATCH 2/3] printk: Add %ptc to safely print a task's comm John Stultz
2011-05-11  0:23   ` John Stultz
2011-05-11  0:51   ` Joe Perches
2011-05-11  0:51     ` Joe Perches
2011-05-11  1:10     ` John Stultz
2011-05-11  1:10       ` John Stultz
2011-05-11  1:16       ` john stultz
2011-05-11  1:16         ` john stultz
2011-05-11  1:20       ` Joe Perches
2011-05-11  1:20         ` Joe Perches
2011-05-12 22:12         ` David Rientjes
2011-05-12 22:12           ` David Rientjes
2011-05-12 22:29           ` Joe Perches
2011-05-12 22:29             ` Joe Perches
2011-05-13 21:56             ` David Rientjes
2011-05-13 21:56               ` David Rientjes
2011-05-12 22:10       ` David Rientjes
2011-05-12 22:10         ` David Rientjes
2011-05-11  9:33   ` Américo Wang
2011-05-11  9:33     ` Américo Wang
2011-05-11 21:02     ` John Stultz
2011-05-11 21:02       ` John Stultz
2011-05-12 10:43       ` Américo Wang
2011-05-12 10:43         ` Américo Wang
2011-05-12 10:45         ` Américo Wang
2011-05-12 10:45           ` Américo Wang
2011-05-12 18:01         ` John Stultz
2011-05-12 18:01           ` John Stultz
2011-05-11 17:36   ` Andi Kleen
2011-05-11 17:36     ` Andi Kleen
2011-05-11 21:04     ` John Stultz [this message]
2011-05-11 21:04       ` John Stultz
2011-05-11  0:23 ` [PATCH 3/3] comm: ext4: Protect task->comm access by using %ptc John Stultz
2011-05-11  0:23   ` John Stultz
2011-05-12 22:14   ` David Rientjes
2011-05-12 22:14     ` David Rientjes
2011-05-12 22:29     ` John Stultz
2011-05-12 22:29       ` John Stultz
2011-05-12 22:34       ` Andrew Morton
2011-05-12 22:34         ` Andrew Morton
  -- strict thread matches above, loose matches on Subject: below --
2011-05-12 23:02 [PATCH 0/3] v3 Improve task->comm locking situation John Stultz
2011-05-12 23:02 ` [PATCH 2/3] printk: Add %ptc to safely print a task's comm John Stultz
2011-05-12 23:02   ` John Stultz
2011-05-16 21:19 [PATCH 0/3] v4 Improve task->comm locking situation John Stultz
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
2011-05-17 20:47 [PATCH 0/3] v5 Improve task->comm locking situation John Stultz
2011-05-17 20:47 ` [PATCH 2/3] printk: Add %ptc to safely print a task's comm John Stultz
2011-05-17 20:47   ` John Stultz
2011-05-17 21:42   ` Jiri Slaby
2011-05-17 21:42     ` Jiri Slaby
2011-05-17 21:52     ` Joe Perches
2011-05-17 21:52       ` Joe Perches
2011-05-17 22:04       ` Jiri Slaby
2011-05-17 22:04         ` Jiri Slaby
2011-05-17 22:17         ` Joe Perches
2011-05-17 22:17           ` Joe Perches
2011-05-17 22:17     ` John Stultz
2011-05-17 22:17       ` John Stultz

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