On Wed, May 16, 2018 at 04:47:54PM +0000, Bart Van Assche wrote: > I think your patch changes the order of changing the request state and > calling mod_timer(). In my patch the request state and the deadline are > updated first and mod_timer() is called afterwards. I think your patch > changes the order of these operations into the following: > (1) __blk_mq_start_request() sets the request deadline. > (2) __blk_mq_start_request() calls __blk_add_timer() which in turn calls > mod_timer(). > (3) __blk_mq_start_request() changes the request state into MQ_RQ_IN_FLIGHT. > > In the unlikely event of a significant delay between (2) and (3) it can > happen that the timer fires and examines and ignores the request because > its state differs from MQ_RQ_IN_FLIGHT. If the request for which this > happened times out its timeout will only be handled the next time > blk_mq_timeout_work() is called. Is this the behavior you intended? We can move the timer manipulation after the change easily I think. It would make sense to add comments explaining the ordering.
