From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752853Ab3IVREW (ORCPT ); Sun, 22 Sep 2013 13:04:22 -0400 Received: from mail-qa0-f53.google.com ([209.85.216.53]:64663 "EHLO mail-qa0-f53.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752434Ab3IVREV (ORCPT ); Sun, 22 Sep 2013 13:04:21 -0400 Date: Sun, 22 Sep 2013 13:04:17 -0400 From: Tejun Heo To: Tomoki Sekiyama Cc: linux-kernel@vger.kernel.org, axboe@kernel.dk, seiji.aguchi@hds.com, vgoyal@redhat.com, majianpeng@gmail.com Subject: Re: [PATCH v2 1/2] elevator: Fix a race in elevator switching and md device initialization Message-ID: <20130922170417.GF30946@htj.dyndns.org> References: <20130830224707.21812.63516.stgit@hds.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130830224707.21812.63516.stgit@hds.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Aug 30, 2013 at 06:47:07PM -0400, Tomoki Sekiyama wrote: > @@ -739,9 +739,17 @@ blk_init_allocated_queue(struct request_queue *q, request_fn_proc *rfn, > > q->sg_reserved_size = INT_MAX; > > + /* Protect q->elevator from elevator_change */ > + mutex_lock(&q->sysfs_lock); > + > /* init elevator */ > - if (elevator_init(q, NULL)) > + if (elevator_init(q, NULL)) { > + mutex_unlock(&q->sysfs_lock); > return NULL; > + } > + > + mutex_unlock(&q->sysfs_lock); > + > return q; > } > EXPORT_SYMBOL(blk_init_allocated_queue); > diff --git a/block/elevator.c b/block/elevator.c > index 668394d..02d4390 100644 > --- a/block/elevator.c > +++ b/block/elevator.c > @@ -186,6 +186,12 @@ int elevator_init(struct request_queue *q, char *name) > struct elevator_type *e = NULL; > int err; > > + /* > + * q->sysfs_lock must be held to provide mutual exclusion between > + * elevator_switch() and here. > + */ > + lockdep_assert_held(&q->sysfs_lock); > + > if (unlikely(q->elevator)) > return 0; Hmm... why aren't we just changing elevator_init() to grab sysfs_lock where necessary? It'd be more consistent with elevator_exit() that way. Thanks. -- tejun