From cf218ddb22acac8b99489bbca95e5eb8341d1d7c Mon Sep 17 00:00:00 2001 From: Can Guo Date: Thu, 20 Aug 2020 12:15:24 +0800 Subject: [PATCH] block: Fix a race in the runtime power management code 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 --- block/blk-pm.c | 16 +++++++++------- 1 file changed, 9 insertions(+), 7 deletions(-) diff --git a/block/blk-pm.c b/block/blk-pm.c index b85234d758f7..385af21d7486 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 +93,13 @@ 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; }