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Tue, 17 Apr 2018 12:01:17 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:60364 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753595AbeDQQBP (ORCPT ); Tue, 17 Apr 2018 12:01:15 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Tejun Heo , Bart Van Assche , Hannes Reinecke , Ming Lei , Christoph Hellwig , Johannes Thumshirn , Oleksandr Natalenko , Martin Steigerwald , Jens Axboe Subject: [PATCH 4.16 36/68] block: Change a rcu_read_{lock,unlock}_sched() pair into rcu_read_{lock,unlock}() Date: Tue, 17 Apr 2018 17:57:49 +0200 Message-Id: <20180417155750.802123392@linuxfoundation.org> X-Mailer: git-send-email 2.17.0 In-Reply-To: <20180417155749.341779147@linuxfoundation.org> References: <20180417155749.341779147@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: stable-owner@vger.kernel.org X-Mailing-List: stable@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: 4.16-stable review patch. If anyone has any objections, please let me know. ------------------ From: Bart Van Assche commit 818e0fa293ca836eba515615c64680ea916fd7cd upstream. scsi_device_quiesce() uses synchronize_rcu() to guarantee that the effect of blk_set_preempt_only() will be visible for percpu_ref_tryget() calls that occur after the queue unfreeze by using the approach explained in https://lwn.net/Articles/573497/. The rcu read lock and unlock calls in blk_queue_enter() form a pair with the synchronize_rcu() call in scsi_device_quiesce(). Both scsi_device_quiesce() and blk_queue_enter() must either use regular RCU or RCU-sched. Since neither the RCU-protected code in blk_queue_enter() nor blk_queue_usage_counter_release() sleeps, regular RCU protection is sufficient. Note: scsi_device_quiesce() does not have to be modified since it already uses synchronize_rcu(). Reported-by: Tejun Heo Fixes: 3a0a529971ec ("block, scsi: Make SCSI quiesce and resume work reliably") Signed-off-by: Bart Van Assche Acked-by: Tejun Heo Cc: Tejun Heo Cc: Hannes Reinecke Cc: Ming Lei Cc: Christoph Hellwig Cc: Johannes Thumshirn Cc: Oleksandr Natalenko Cc: Martin Steigerwald Cc: stable@vger.kernel.org # v4.15 Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman --- block/blk-core.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- a/block/blk-core.c +++ b/block/blk-core.c @@ -827,7 +827,7 @@ int blk_queue_enter(struct request_queue bool success = false; int ret; - rcu_read_lock_sched(); + rcu_read_lock(); if (percpu_ref_tryget_live(&q->q_usage_counter)) { /* * The code that sets the PREEMPT_ONLY flag is @@ -840,7 +840,7 @@ int blk_queue_enter(struct request_queue percpu_ref_put(&q->q_usage_counter); } } - rcu_read_unlock_sched(); + rcu_read_unlock(); if (success) return 0;