On 3/12/21 2:17 PM, Linus Torvalds wrote: > On Fri, Mar 12, 2021 at 11:48 AM Jens Axboe <axboe@xxxxxxxxx> wrote: >> >> - Make IO threads unfreezable by default, on account of a bug report >> that had them spinning on resume. Honestly not quite sure why thawing >> leaves us with a perpetual signal pending (causing the spin), but for >> now make them unfreezable like there were in 5.11 and prior. > > That "not quite sure" doesn't exactly give my the warm and fuzzies, > but not being new is ok, I guess. But I'd really like you to try to > figure out what is actually going on. Oh I agree, which is why I wanted to bring it up as I do feel like we're just working around this issue. > I'm _guessing_ it's just that now those threads are user threads, and > then the freezing logic expects them to freeze/thaw using a signal > machinery or something like that. And that doesn't work when there is > no signal handling for those threads. > > But it would be good to _know_. That's very much my guess too, since the symptom is that we loop all the time because we think there's a signal pending. I am investigating it and reached out to Rafael to try and figure this out, but at the same time I did not want to have an -rc3 that caused resume issues for users. Hence the "let's just disable freezing for now so that things work, get it fixed for real when we can" kind of solution. -- Jens Axboe
