On Thu, Aug 02, 2018 at 05:08:38PM +0100, Al Viro wrote: > On Thu, Aug 02, 2018 at 06:08:16PM +0200, Christoph Hellwig wrote: > > On Thu, Aug 02, 2018 at 05:00:32PM +0100, Al Viro wrote: > > > BTW, what happens if we insert into one queue and immediately get > > > woken up, even before the damn thing gets to the end of ->poll(), > > > which proceeds to call poll_wait() again (on another queue)? > > > AFAICS, apt.error will be set by the second callback and completely > > > ignored. And so will the return value of ->poll()... > > > > > > Sigh... Analysis of that thing is bloody painful, mostly because > > > it's hard to describe the state... > > > > That's the problem with the ->poll interface. We call it, then > > have magic happen underneath where it might or might not get added > > to one (or more if we didn't exclude that) waitqueues, and might > > have actually been worken before return. I can't really think of > > a good way to do that entirely sanely. > > > > Best I can think of is to only allow using file ops that do keyed > > wakeups and rely on the keyed wakeups alone. I've started coming > > up with a version of that, but it won't be until tomorrow at least > > that I can post it. > > What does it buy you? You still have to deal with trylock failures > in wakeup... But we'll never re-add an iocb once it has been removed from the waitqueue.
