[PATCH 5.10 13/63] scsi: block: Fix a race in the runtime power management code

Greg Kroah-Hartman
2021-01-04T16:09:03Z

From: Bart Van Assche <bvanassche@acm.org>

commit fa4d0f1992a96f6d7c988ef423e3127e613f6ac9 upstream.

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.

Link: https://lore.kernel.org/r/20201209052951.16136-2-bvanassche@acm.org
Fixes: 986d413b7c15 ("blk-mq: Enable support for runtime power management")
Cc: Ming Lei <ming.lei@redhat.com>
Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: stable <stable@vger.kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Jens Axboe <axboe@kernel.dk>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Acked-by: Stanley Chu <stanley.chu@mediatek.com>
Co-developed-by: Can Guo <cang@codeaurora.org>
Signed-off-by: Can Guo <cang@codeaurora.org>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
block/blk-pm.c | 15 +++++++++------
1 file changed, 9 insertions(+), 6 deletions(-)

--- a/block/blk-pm.c
+++ b/block/blk-pm.c
@@ -67,6 +67,10 @@ int blk_pre_runtime_suspend(struct reque

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 reque
/* 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;
}