On 24/02/17 02:36, Keith Busch wrote:
If the block layer has entered requests and gets a CPU hot plug event prior to the resume event, it will wait for those requests to exit. If the nvme driver is shutting down, it will not start the queues back up, preventing forward progress. To fix that, this patch freezes the request queues when the driver intends to shut down the controller so that no new requests may enter. After the controller has been disabled, the queues will be restarted to force all entered requests to end in failure so that blk-mq's hot cpu notifier may progress. To ensure the queue usage count is 0 on a shutdown, the driver waits for freeze to complete before completing the controller shutdown.
Keith, can you explain (again) for me why is the freeze_wait must happen after the controller has been disabled, instead of starting the queues and waiting right after freeze start?
