Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757256Ab1ELKpI (ORCPT ); Thu, 12 May 2011 06:45:08 -0400 Received: from mail-vw0-f46.google.com ([209.85.212.46]:38142 "EHLO mail-vw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757084Ab1ELKpG convert rfc822-to-8bit (ORCPT ); Thu, 12 May 2011 06:45:06 -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=ZqwL+IFtsF7UOyppOtFDGHzukFqQKT5/SkexSnFgTa78/BGm+T1hncTjXLIGFbx6S/ TmyQo8jAeFM1eAQrsoBdmoS10pyT8fvMfiFoJicoyneIxgGnCsuSM1TGj++NnAdsqYNG EmxYuPF1I7bf8jBThk6Wv1Dpu32ZQh7Pmgd1Q= MIME-Version: 1.0 In-Reply-To: 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 18:45:05 +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: 1769 Lines: 37 On Thu, May 12, 2011 at 6:43 PM, Américo Wang wrote: > 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? > Ahhh, never mind, I see the points now... Then it is fine. :) -- 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/