>>>>> "Bart" == Bart Van Assche <Bart.VanAssche@xxxxxxx> writes: Bart> On Mon, 2018-01-29 at 16:44 -0500, Mike Snitzer wrote: >> But regardless of which wins the race, the queue will have been run. >> Which is all we care about right? Bart> Running the queue is not sufficient. With this patch applied it can happen Bart> that the block driver returns BLK_STS_DEV_RESOURCE, that the two or more Bart> concurrent queue runs finish before sufficient device resources are available Bart> to execute the request and that blk_mq_delay_run_hw_queue() does not get Bart> called at all. If no other activity triggers a queue run, e.g. request Bart> completion, this will result in a queue stall. Doesn't this argue that you really want some sort of completions to be run in this case instead? Instead of busy looping or waiting for a set amount of time, just fire off a callback to run once you have the resources available, no? I can't provide any code examples, I don't know the code base nearly well enough. John
