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From: Bart Van Assche <bvanassche@acm.org>
To: "Martin K . Petersen" <martin.petersen@oracle.com>
Cc: "James E . J . Bottomley" <jejb@linux.vnet.ibm.com>,
	Jens Axboe <axboe@kernel.dk>, Christoph Hellwig <hch@lst.de>,
	Hannes Reinecke <hare@suse.de>, Ming Lei <ming.lei@redhat.com>,
	linux-scsi@vger.kernel.org, linux-block@vger.kernel.org,
	Bart Van Assche <bvanassche@acm.org>,
	Alan Stern <stern@rowland.harvard.edu>,
	Stanley Chu <stanley.chu@mediatek.com>,
	"Rafael J . Wysocki" <rafael.j.wysocki@intel.com>,
	stable <stable@vger.kernel.org>, Can Guo <cang@codeaurora.org>
Subject: [PATCH v5 1/8] block: Fix a race in the runtime power management code
Date: Tue,  8 Dec 2020 21:29:44 -0800
Message-ID: <20201209052951.16136-2-bvanassche@acm.org> (raw)
In-Reply-To: <20201209052951.16136-1-bvanassche@acm.org>

With the current implementation the following race can happen:
* blk_pre_runtime_suspend() calls blk_freeze_queue_start() and
  blk_mq_unfreeze_queue().
* blk_queue_enter() calls blk_queue_pm_only() and that function returns
  true.
* blk_queue_enter() calls blk_pm_request_resume() and that function does
  not call pm_request_resume() because the queue runtime status is
  RPM_ACTIVE.
* blk_pre_runtime_suspend() changes the queue status into RPM_SUSPENDING.

Fix this race by changing the queue runtime status into RPM_SUSPENDING
before switching q_usage_counter to atomic mode.

Acked-by: Alan Stern <stern@rowland.harvard.edu>
Acked-by: Stanley Chu <stanley.chu@mediatek.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Jens Axboe <axboe@kernel.dk>
Cc: Ming Lei <ming.lei@redhat.com>
Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: stable <stable@vger.kernel.org>
Fixes: 986d413b7c15 ("blk-mq: Enable support for runtime power management")
Signed-off-by: Can Guo <cang@codeaurora.org>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---
 block/blk-pm.c | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/block/blk-pm.c b/block/blk-pm.c
index b85234d758f7..17bd020268d4 100644
--- a/block/blk-pm.c
+++ b/block/blk-pm.c
@@ -67,6 +67,10 @@ int blk_pre_runtime_suspend(struct request_queue *q)
 
 	WARN_ON_ONCE(q->rpm_status != RPM_ACTIVE);
 
+	spin_lock_irq(&q->queue_lock);
+	q->rpm_status = RPM_SUSPENDING;
+	spin_unlock_irq(&q->queue_lock);
+
 	/*
 	 * Increase the pm_only counter before checking whether any
 	 * non-PM blk_queue_enter() calls are in progress to avoid that any
@@ -89,15 +93,14 @@ int blk_pre_runtime_suspend(struct request_queue *q)
 	/* Switch q_usage_counter back to per-cpu mode. */
 	blk_mq_unfreeze_queue(q);
 
-	spin_lock_irq(&q->queue_lock);
-	if (ret < 0)
+	if (ret < 0) {
+		spin_lock_irq(&q->queue_lock);
+		q->rpm_status = RPM_ACTIVE;
 		pm_runtime_mark_last_busy(q->dev);
-	else
-		q->rpm_status = RPM_SUSPENDING;
-	spin_unlock_irq(&q->queue_lock);
+		spin_unlock_irq(&q->queue_lock);
 
-	if (ret)
 		blk_clear_pm_only(q);
+	}
 
 	return ret;
 }

  reply index

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-12-09  5:29 [PATCH v5 0/8] Rework runtime suspend and SPI domain validation Bart Van Assche
2020-12-09  5:29 ` Bart Van Assche [this message]
2020-12-09  5:29 ` [PATCH v5 2/8] block: Introduce BLK_MQ_REQ_PM Bart Van Assche
2020-12-09  6:06   ` Can Guo
2020-12-09  5:29 ` [PATCH v5 3/8] ide: Do not set the RQF_PREEMPT flag for sense requests Bart Van Assche
2020-12-09  5:29 ` [PATCH v5 4/8] ide: Mark power management requests with RQF_PM instead of RQF_PREEMPT Bart Van Assche
2020-12-09  5:29 ` [PATCH v5 5/8] scsi_transport_spi: Set RQF_PM for domain validation commands Bart Van Assche
2020-12-09  7:34   ` Hannes Reinecke
2020-12-09  5:29 ` [PATCH v5 6/8] scsi: Only process PM requests if rpm_status != RPM_ACTIVE Bart Van Assche
2020-12-09  6:06   ` Can Guo
2020-12-09  5:29 ` [PATCH v5 7/8] block: Remove RQF_PREEMPT and BLK_MQ_REQ_PREEMPT Bart Van Assche
2020-12-09  6:05   ` Can Guo
2020-12-09  5:29 ` [PATCH v5 8/8] block: Do not accept any requests while suspended Bart Van Assche
2020-12-09  6:04   ` Can Guo
2020-12-09  7:36   ` Hannes Reinecke
2020-12-09 16:44 ` [PATCH v5 0/8] Rework runtime suspend and SPI domain validation Martin K. Petersen

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