Re: [PATCH v2 1/9] block: Fix a race in the runtime power management code

On Sun, Nov 15, 2020 at 07:04:51PM -0800, Bart Van Assche wrote:

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.

Looks good,

Reviewed-by: Christoph Hellwig hch@lst.de