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. This problem was fixed on -rt using a -rt specific lock mechanism, but the problem still exist in the non-rt kernel. Btw, this is just an example of side effects of the starvation of non-rt-tasks. We can have more examples... -- Daniel -- 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
