On Mon, 7 Nov 2016 19:49:03 +0100 Daniel Bristot de Oliveira <daniel@xxxxxxxxxx> wrote: > On 11/07/2016 07:32 PM, Steven Rostedt wrote: > >> Excellent this would improve the situation with deadlocks as a result of > >> > cgroup_locks not being released due to lack of workqueue processing. > > ?? What deadlocks do you see? I mean, can you show the situation that > > throttling RT tasks will cause deadlock? > > > > Sorry, but I'm just not seeing it. > > It is not a deadlock in the theoretical sense of the word, but it is > more a side effect of the starvation - that looks like a deadlock. > > There is a case where the removal of a cgroup dir calls > lru_add_drain_all(), that might schedule a kworker in the CPU that is > running the spinning-rt task. The kworker will starve - because they are > SCHED_OTHER by design, the lru_add_drain_all() will wait forever while > holding the cgroup lock and this will cause a lot of problems on other > tasks. I understand the issue with not throttling an RT task, but this patch is about not not throttling! That is, what scenario is there that will cause a "deadlock" or deadlock like to happen when we *do* throttle, where not throttling will work better, as this patch would have? -- Steve -- To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
