From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx161.postini.com [74.125.245.161]) by kanga.kvack.org (Postfix) with SMTP id 3B3B36B00FF for ; Sat, 24 Mar 2012 08:44:48 -0400 (EDT) Message-ID: <1332593021.16159.27.camel@twins> Subject: Re: [PATCH 01/10] cpu: Introduce clear_tasks_mm_cpumask() helper From: Peter Zijlstra Date: Sat, 24 Mar 2012 13:43:41 +0100 In-Reply-To: <20120324102751.GA29067@lizard> References: <20120324102609.GA28356@lizard> <20120324102751.GA29067@lizard> Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: quoted-printable Mime-Version: 1.0 Sender: owner-linux-mm@kvack.org List-ID: To: Anton Vorontsov Cc: Andrew Morton , Oleg Nesterov , Russell King , Mike Frysinger , Benjamin Herrenschmidt , Richard Weinberger , Paul Mundt , KOSAKI Motohiro , John Stultz , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, uclinux-dist-devel@blackfin.uclinux.org, linuxppc-dev@lists.ozlabs.org, linux-sh@vger.kernel.org, user-mode-linux-devel@lists.sourceforge.net, linux-mm@kvack.org On Sat, 2012-03-24 at 14:27 +0400, Anton Vorontsov wrote: > +void clear_tasks_mm_cpumask(int cpu) > +{ > + struct task_struct *p; > + > + read_lock(&tasklist_lock); > + for_each_process(p) { > + struct task_struct *t; > + > + t =3D find_lock_task_mm(p); > + if (!t) > + continue; > + cpumask_clear_cpu(cpu, mm_cpumask(t->mm)); > + task_unlock(t); > + } > + read_unlock(&tasklist_lock); > +}=20 Why bother with the tasklist_lock at all anymore, afaict you could use rcu_read_lock() here. This all is called after the cpu is taken down and marked offline, so its not like new tasks will ever get this cpu set in their mm mask. -- 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