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block: Fix a race in the runtime power management code

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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.

Change-Id: I5a2c842b959b8c57730b12e4f372abc515a8c8ab
Signed-off-by: Can Guo <cang@codeaurora.org>
This commit is contained in:
Can Guo 2020-08-20 12:15:24 +08:00
commit cf218ddb22
1 changed files with 9 additions and 7 deletions
Download patch file Download diff file Expand all files Collapse all files

16
block/blk-pm.c
View file

@ -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 +93,13 @@ 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);
if (ret)
spin_unlock_irq(&q->queue_lock);
blk_clear_pm_only(q);
}
return ret;
}