From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail191.messagelabs.com (mail191.messagelabs.com [216.82.242.19]) by kanga.kvack.org (Postfix) with ESMTP id ABB306B0024 for ; Wed, 11 May 2011 17:03:17 -0400 (EDT) Received: from d03relay02.boulder.ibm.com (d03relay02.boulder.ibm.com [9.17.195.227]) by e35.co.us.ibm.com (8.14.4/8.13.1) with ESMTP id p4BKkI7J017016 for ; Wed, 11 May 2011 14:46:18 -0600 Received: from d03av02.boulder.ibm.com (d03av02.boulder.ibm.com [9.17.195.168]) by d03relay02.boulder.ibm.com (8.13.8/8.13.8/NCO v9.1) with ESMTP id p4BL35Dp143610 for ; Wed, 11 May 2011 15:03:07 -0600 Received: from d03av02.boulder.ibm.com (loopback [127.0.0.1]) by d03av02.boulder.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id p4BF2b3r004554 for ; Wed, 11 May 2011 09:02:38 -0600 Subject: Re: [PATCH 2/3] printk: Add %ptc to safely print a task's comm From: John Stultz In-Reply-To: References: <1305073386-4810-1-git-send-email-john.stultz@linaro.org> <1305073386-4810-3-git-send-email-john.stultz@linaro.org> Content-Type: text/plain; charset="UTF-8" Date: Wed, 11 May 2011 14:02:56 -0700 Message-ID: <1305147776.2883.1.camel@work-vm> Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org List-ID: To: =?ISO-8859-1?Q?Am=E9rico?= Wang Cc: LKML , Ted Ts'o , KOSAKI Motohiro , David Rientjes , Dave Hansen , Andrew Morton , linux-mm@kvack.org On Wed, 2011-05-11 at 17:33 +0800, AmA(C)rico Wang wrote: > On Wed, May 11, 2011 at 8:23 AM, John Stultz wrote: > > 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); > > > > Why do you hide current->comm behide printk? > How is this better than printk("%s: ....", task_comm(current)) ? So to properly access current->comm, you need to hold the task-lock (or with my new patch set, the comm_lock). Rather then adding locking to all the call sites that printk("%s ...", current->comm), I'm suggesting we add a new %ptc method which will handle the locking for you. thanks -john -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org