On 1/8/21 8:58 AM, Al Viro wrote: > On Fri, Jan 08, 2021 at 08:13:25AM -0700, Jens Axboe wrote: >>> Anyway, bedtime for me; right now it looks like at least for task == >>> current we always want TWA_SIGNAL. I'll look into that more tomorrow >>> when I get up, but so far it smells like switching everything to >>> TWA_SIGNAL would be the right thing to do, if not going back to bool >>> notify for task_work_add()... >> >> Before the change, the fact that we ran task_work off get_signal() and >> thus processed even non-notify work in that path was a bit of a mess, >> imho. If you have work that needs processing now, in the same manner as >> signals, then you really should be using TWA_SIGNAL. For this pipe case, >> and I'd need to setup and reproduce it again, the task must have a >> signal pending and that would have previously caused the task_work to >> run, and now it does not. TWA_RESUME technically didn't change its >> behavior, it's still the same notification type, we just don't run >> task_work unconditionally (regardless of notification type) from >> get_signal(). > > It sure as hell did change behaviour. Think of the effect of getting > hit with SIGSTOP. That's what that "bit of a mess" had been about. > Work done now vs. possibly several days later when SIGCONT finally > gets sent. > >> I think the main question here is if we want to re-instate the behavior >> of running task_work off get_signal(). I'm leaning towards not doing >> that and ensuring that callers that DO need that are using TWA_SIGNAL. > > Can you show the callers that DO NOT need it? OK, so here's my suggestion: 1) For 5.11, we just re-instate the task_work run in get_signal(). This will make TWA_RESUME have the exact same behavior as before. 2) For 5.12, I'll prepare a patch that collapses TWA_RESUME and TWA_SIGNAL, turning it into a bool again (notify or no notify). How does that sound? -- Jens Axboe
