On Tue, Jan 30, 2018 at 01:11:22AM +0000, Bart Van Assche wrote: > On Tue, 2018-01-30 at 09:07 +0800, Ming Lei wrote: > > On Mon, Jan 29, 2018 at 04:48:31PM +0000, Bart Van Assche wrote: > > > - It is easy to fix this race inside the block layer, namely by using > > > call_rcu() inside the blk_mq_delay_run_hw_queue() implementation to > > > postpone the queue rerunning until after the request has been added back to > > > the dispatch list. > > > > It is just easy to say, can you cook a patch and fix all drivers first? > > Please reread what I wrote. I proposed to change the blk_mq_delay_run_hw_queue() > IMPLEMENTATION such that the callers do not have to be modified. Please take a look at drivers, when BLK_STS_RESOURCE is returned, who will call blk_mq_delay_run_hw_queue() for drivers? > > > [ ... ] Later, you admitted you understood the patch wrong. [ ... ] > > That's nonsense. I never wrote that. Believe it or not, follows the link and your reply: https://marc.info/?l=dm-devel&m=151672694508389&w=2 > So what is wrong with this way? >Sorry, I swapped BLK_STS_DEV_RESOURCE and BLK_STS_RESOURCE accidentally in my >reply. What I meant is that changing a blk_mq_delay_run_hw_queue() call followed >by return BLK_STS_RESOURCE into BLK_STS_DEV_RESOURCE is wrong and introduces a >race condition in code where there was no race condition. > >Bart. -- Ming
