Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757241Ab1ELKnJ (ORCPT ); Thu, 12 May 2011 06:43:09 -0400 Received: from mail-vw0-f46.google.com ([209.85.212.46]:53892 "EHLO mail-vw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756023Ab1ELKnH convert rfc822-to-8bit (ORCPT ); Thu, 12 May 2011 06:43:07 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; b=oVNf8zLOc4k40Z5DnlTk9D0zHerz8Qd370+hFSD4FW3PYLCprdnS0Y5i4jz0AWZcRT pv7y7DVlxIm9uyYHPD0iEZdvIYhEY5kd/P4bk4osihcOfJoA8ugQV5EumaQvui8SgdZP uc2VLIVadeSt4piUGkyEnxsloLOa4nMTscZLM= MIME-Version: 1.0 In-Reply-To: <1305147776.2883.1.camel@work-vm> References: <1305073386-4810-1-git-send-email-john.stultz@linaro.org> <1305073386-4810-3-git-send-email-john.stultz@linaro.org> <1305147776.2883.1.camel@work-vm> Date: Thu, 12 May 2011 18:43:05 +0800 Message-ID: Subject: Re: [PATCH 2/3] printk: Add %ptc to safely print a task's comm From: =?UTF-8?Q?Am=C3=A9rico_Wang?= To: John Stultz Cc: LKML , "Ted Ts'o" , KOSAKI Motohiro , David Rientjes , Dave Hansen , Andrew Morton , linux-mm@kvack.org Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1693 Lines: 41 On Thu, May 12, 2011 at 5:02 AM, John Stultz wrote: > On Wed, 2011-05-11 at 17:33 +0800, Américo 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. > Sorry, I meant why not adding the locking into a wrapper function, probably get_task_comm() and let the users to call it directly? Why is %ptc better than char comm[...]; get_task_comm(comm, current); printk("%s: ....", comm); ? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/