Messages in this thread | | | Date | Fri, 8 Jul 2022 15:06:14 -0400 | From | Steven Rostedt <> | Subject | Re: [PATCH v3] sched/rt: fix bad task migration for rt tasks |
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On Sat, 09 Jul 2022 02:19:42 +0800 Schspa Shi <schspa@gmail.com> wrote:
> Yes, it's what I did in the V1 patch. > Link: https://lore.kernel.org/all/20220623182932.58589-1-schspa@gmail.com/ > > But I think it's not the best solution for this problem. > In these scenarios, we still have a chance to make the task run faster > by retrying to retry to push the currently running task on this CPU away. > > There is more details on V2 patch's replay message. > Link: https://lore.kernel.org/all/CAMA88TrZ-o4W81Yfw9Wcs3ghoxwpeAKtFejtMTt78GNB0tKaSA@mail.gmail.com/#t
The thing is, this situation can only happen if we release the rq lock in find_lock_lowest_rq(), and we should not be checking for it in the other cases.
Perhaps add the check in find_lock_lowest_rq() and also in the !lowest_rq case do:
task = pick_next_pushable_task(rq); if (task == next_task) { + /* + * If next task has now disabled migrating, see if we + * can push the current task. + */ + if (unlikely(is_migrate_disabled(task))) + goto retry; /* * The task hasn't migrated, and is still the next * eligible task, but we failed to find a run-queue * to push it to. Do not retry in this case, since * other CPUs will pull from us when ready. */ goto out; }
-- Steve
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