From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AIpwx486ZDQZKzVKVHwR7V+XfX62Oh4T8Me56BWGx8e9DjiZUMwB3S98ieTftz+zemktb83118Y0 ARC-Seal: i=1; a=rsa-sha256; t=1523981071; cv=none; d=google.com; s=arc-20160816; b=otwdUwoH6NDJOhfsDSK1iwoN7MvOqSrB0+FbSOFsBuMz14fJ4WHhWXOjFbA22EfrKk lu2gf79rMTZB859Qyb0X99x18CSHXWPyzBJ5CusKxNZIymPRnFmNXo9AaJsZ9nr+QYI/ SkQ4ZJuYtcwrXYeZYs9qMf63cAJHtTL7TDiACvNA52TeVXzKN25CUk5Pok359FVaM6Td +dDFmhQ1k+XUWRo1aYNsQyfd3uQNJNP8SLK21GuaglWzqNMiNHbfgKyhk7Yp9Yb+TCwz FrXu9Y1sd8n3B+xWyZ1r/bN5ATqPcasevyF4pQixvekZIgWWjvJx4nkudZm781Sl+6tV Yf/Q== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=mime-version:user-agent:references:in-reply-to:message-id:date :subject:cc:to:from:arc-authentication-results; bh=MMGiR3xO3Z7g6xX3cQ6iNhZ2c6nrkn8O8HDNeaS+z70=; b=DEGZpFqykD1SMCMq+VYEdvSnDXDIQx4vHAzx8m4MI8xetyEOpua6C/OU4zWOwhlPuR dqmxshH0xt2bzmgLK9nQBVktA9ka4lKtDjXww7lO+Pmbh/0cYUOE7TJ//0w0cvv9qW0L UwK+JaVCUxOd1hE5owrKEa9+TUVhqy3DKlpfGbIs/BdwG9bHG3taExQ36KbcLK5TvEbK Yhi5oVPUUh+WKGPmbce91V0XfEEn5Kwt+ojawwxf3Ph9Q46CGaRYnt+9qzezw8gckOFu BAcb+xusnzkK8GNJCw9XNZXSfKjQcAXf0iGEtChV+wAB3qHUnjAxzUUxEisPY6r3lhhe YbUA== ARC-Authentication-Results: i=1; mx.google.com; spf=softfail (google.com: domain of transitioning gregkh@linuxfoundation.org does not designate 46.44.180.42 as permitted sender) smtp.mailfrom=gregkh@linuxfoundation.org Authentication-Results: mx.google.com; spf=softfail (google.com: domain of transitioning gregkh@linuxfoundation.org does not designate 46.44.180.42 as permitted sender) smtp.mailfrom=gregkh@linuxfoundation.org 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 4.15 28/53] block: Change a rcu_read_{lock,unlock}_sched() pair into rcu_read_{lock,unlock}() Date: Tue, 17 Apr 2018 17:58:53 +0200 Message-Id: <20180417155724.531278623@linuxfoundation.org> X-Mailer: git-send-email 2.17.0 In-Reply-To: <20180417155723.091120060@linuxfoundation.org> References: <20180417155723.091120060@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-LABELS: =?utf-8?b?IlxcU2VudCI=?= X-GMAIL-THRID: =?utf-8?q?1598009769995705477?= X-GMAIL-MSGID: =?utf-8?q?1598009976278568492?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: 4.15-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 @@ -823,7 +823,7 @@ 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 @@ -836,7 +836,7 @@ 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;