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

Christoph Hellwig
2020-11-16T17:14:59Z

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>