linux-kernel - Re: [PATCH 2/3] printk: Add %ptc to safely print a task's comm

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Message-ID: <m2sjsli1ft.fsf@firstfloor.org>
Date:	Wed, 11 May 2011 10:36:54 -0700
From:	Andi Kleen <andi@...stfloor.org>
To:	John Stultz <john.stultz@...aro.org>
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 2/3] printk: Add %ptc to safely print a task's comm

John Stultz <john.stultz@...aro.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.

-Andi

-- 
ak@...ux.intel.com -- Speaking for myself only
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