Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751879Ab0KYImL (ORCPT ); Thu, 25 Nov 2010 03:42:11 -0500 Received: from casper.infradead.org ([85.118.1.10]:33779 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751737Ab0KYImJ convert rfc822-to-8bit (ORCPT ); Thu, 25 Nov 2010 03:42:09 -0500 Subject: Re: rcu_read_lock/unlock protect find_task_by_vpid call in migrate_pages From: Peter Zijlstra To: KOSAKI Motohiro Cc: Dave Jones , Linux Kernel , linux-mm@vger.kernel.org, Andrew Morton , tglx , Oleg Nesterov , "Paul E. McKenney" In-Reply-To: <20101125095012.F446.A69D9226@jp.fujitsu.com> References: <20101125003339.GB31301@redhat.com> <20101125095012.F446.A69D9226@jp.fujitsu.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8BIT Date: Thu, 25 Nov 2010 09:42:21 +0100 Message-ID: <1290674541.2072.564.camel@laptop> Mime-Version: 1.0 X-Mailer: Evolution 2.30.3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1262 Lines: 40 On Thu, 2010-11-25 at 09:50 +0900, KOSAKI Motohiro wrote: > Hi > > > Signed-off-by: Dave Jones > > > > diff --git a/mm/mempolicy.c b/mm/mempolicy.c > > index 4a57f13..2f0f55b 100644 > > --- a/mm/mempolicy.c > > +++ b/mm/mempolicy.c > > @@ -1308,6 +1308,7 @@ SYSCALL_DEFINE4(migrate_pages, pid_t, pid, unsigned long, maxnode, > > > > /* Find the mm_struct */ > > read_lock(&tasklist_lock); > > + rcu_read_lock(); > > task = pid ? find_task_by_vpid(pid) : current; > > if (!task) { > > read_unlock(&tasklist_lock); > > @@ -1315,6 +1316,7 @@ SYSCALL_DEFINE4(migrate_pages, pid_t, pid, unsigned long, maxnode, > > goto out; > > } > > mm = get_task_mm(task); > > + rcu_read_unlock(); > > read_unlock(&tasklist_lock); > > > > err = -EINVAL; > > Thanks reporting. but mmotm seems already has the same patch. Another one,... again: Do we still need the tasklist_lock in this case? Also, why is that think complaining, surely the tasklist_lock pins any and all PID objects? -- 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/