Messages in this thread | | | Date | Tue, 27 Sep 2022 11:25:22 -0400 | Subject | Re: locking/rwsem: RT throttling issue due to RT task hogging the cpu | From | Waiman Long <> |
| |
On 9/20/22 12:19, Mukesh Ojha wrote: > Hi, > > We are observing one issue where, sem->owner is not set and > sem->count=6 [1] which means both RWSEM_FLAG_WAITERS and > RWSEM_FLAG_HANDOFF bits are set. And if unfold the sem->wait_list we > see the following order of process waiting [2] where [a] is waiting > for write, while [b],[c] are waiting for read and [d] is the RT task > for which waiter.handoff_set=true and it is continuously running on > cpu7 and not letting the first write waiter [a] on cpu7. > > [1] > > sem = 0xFFFFFFD57DDC6680 -> ( > count = (counter = 6), > owner = (counter = 0), > > [2] > > [a] kworker/7:0 pid: 32516 ==> [b] iptables-restor pid: 18625 ==> > [c]HwBinder:1544_3 pid: 2024 ==> [d] RenderEngine pid: 2032 cpu: 7 > prio:97 (RT task) > > > Sometime back, Waiman has suggested this which could help in RT task > leaving the cpu. > > https://lore.kernel.org/all/8c33f989-8870-08c6-db12-521de634b34e@redhat.com/ > > Sorry for the late reply. There is now an alternative way of dealing with this RT task hogging issue with the commit 48dfb5d2560d ("locking/rwsem: Disable preemption while trying for rwsem lock"). Could you try it to see if it can address your problem?
Thanks, Longman
| |