Messages in this thread | | | Date | Tue, 22 Mar 2022 13:59:20 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH v2 1/6] perf/core: Fix incosistency between cgroup sched_out and sched_in |
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On Tue, Mar 22, 2022 at 08:08:29PM +0800, Chengming Zhou wrote: > There is a race problem that can trigger WARN_ON_ONCE(cpuctx->cgrp) > in perf_cgroup_switch(). > > CPU1 CPU2 > (in context_switch) (attach running task) > perf_cgroup_sched_out(prev, next) > cgrp1 == cgrp2 is True > next->cgroups = cgrp3 > perf_cgroup_attach() > perf_cgroup_sched_in(prev, next) > cgrp1 == cgrp3 is False > > The commit a8d757ef076f ("perf events: Fix slow and broken cgroup > context switch code") would save cpuctx switch out/in when the > perf_cgroup of "prev" and "next" are the same. > > But perf_cgroup of task can change in concurrent with context_switch.
Can you clarify? IIRC then a task changes cgroup it goes throught the whole ->attach() dance, and that serializes against the context switch code.
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