On Wed, Jan 31 2024 at 6:19P -0500, Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote: > On Wed, 31 Jan 2024 at 13:32, Tejun Heo <tj@xxxxxxxxxx> wrote: > > > > I don't know, so just did the dumb thing. If the caller always guarantees > > that the work items are never queued at the same time, reusing is fine. > > So the reason I thought it would be a good cleanup to introduce that > "atomic" workqueue thing (now "bh") was that this case literally has a > switch between "use tasklets' or "use workqueues". > > So it's not even about "reusing" the workqueue, it's literally a > matter of making it always just use workqueues, and the switch then > becomes just *which* workqueue to use - system or bh. DM generally always use dedicated workqueues instead of the system. The dm-crypt tasklet's completion path did punt to the workqueue otherwise there was use-after-free of the per-bio-data that included the tasklet. And for verity there was fallback to workqueue if tasklet-based verification failed. Didn't inspire confidence. > In fact, I suspect there is very little reason ever to *not* just use > the bh one, and even the switch could be removed. > > Because I think the only reason the "workqueue of tasklet" choice > existed in the first place was that workqueues were the "proper" data > structure, and the tasklet case was added later as a latency hack, and > everybody knew that tasklets were deprecated. Correct, abusing tasklets was a very contrived latency optimization. Happy to see it all go away! (hindsight: it never should have gone in). Mike
