From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753179Ab3IWUMM (ORCPT ); Mon, 23 Sep 2013 16:12:12 -0400 Received: from usindpps03.hds.com ([207.126.252.16]:53145 "EHLO usindpps03.hds.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750703Ab3IWUMK convert rfc822-to-8bit (ORCPT ); Mon, 23 Sep 2013 16:12:10 -0400 From: Tomoki Sekiyama To: Tejun Heo CC: "linux-kernel@vger.kernel.org" , "axboe@kernel.dk" , Seiji Aguchi , "vgoyal@redhat.com" , "majianpeng@gmail.com" Subject: Re: [PATCH v2 1/2] elevator: Fix a race in elevator switching and md device initialization Thread-Topic: [PATCH v2 1/2] elevator: Fix a race in elevator switching and md device initialization Thread-Index: AQHOpdLdNzajY7OslkaUETgfqPSrrZnSYvOAgAGDsgA= Date: Mon, 23 Sep 2013 20:11:55 +0000 Message-ID: In-Reply-To: <20130922170417.GF30946@htj.dyndns.org> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [10.74.73.11] Content-Type: text/plain; charset="us-ascii" Content-ID: <13862237B546AA4EB7E56DAE4CED6BE6@hds.com> Content-Transfer-Encoding: 8BIT MIME-Version: 1.0 X-Proofpoint-SPF-Result: pass X-Proofpoint-SPF-Record: v=spf1 mx ip4:207.126.244.0/26 ip4:207.126.252.0/25 include:mktomail.com include:cloud.hds.com ~all X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:5.10.8794,1.0.431,0.0.0000 definitions=2013-09-23_03:2013-09-22,2013-09-23,1970-01-01 signatures=0 X-Proofpoint-Spam-Details: rule=notspam policy=outbound_policy score=0 spamscore=0 suspectscore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=7.0.1-1305240000 definitions=main-1309230111 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Tejun, Thank you for the review. On 9/22/13 13:04 , "Tejun Heo" wrote: >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? The locking cannot be moved into elevator_init() because it is called from elevator_switch() path, where the request_queue's sysfs_lock is already taken. > It'd be more consistent with elevator_exit() that way. What elevator_exit() locks is elevator_queue's sysfs_lock, not request_queue's sysfs_lock. What we need here is request_queue's sysfs_lock. >Thanks. > >-- >Tejun Thanks, Tomoki Sekiyama