From: Peter Zijlstra <peterz@infradead.org>
To: Chengming Zhou <zhouchengming@bytedance.com>
Cc: mingo@redhat.com, acme@kernel.org, mark.rutland@arm.com,
alexander.shishkin@linux.intel.com, jolsa@kernel.org,
namhyung@kernel.org, eranian@google.com,
linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org,
duanxiongchun@bytedance.com, songmuchun@bytedance.com
Subject: Re: [PATCH v2 1/6] perf/core: Fix incosistency between cgroup sched_out and sched_in
Date: Tue, 22 Mar 2022 13:59:20 +0100 [thread overview]
Message-ID: <YjnIKCIRV+ePJVCN@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20220322120834.98637-2-zhouchengming@bytedance.com>
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.
next prev parent reply other threads:[~2022-03-22 12:59 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-22 12:08 [PATCH v2 0/6] perf/core: Fixes and cleanup for cgroup events Chengming Zhou
2022-03-22 12:08 ` [PATCH v2 1/6] perf/core: Fix incosistency between cgroup sched_out and sched_in Chengming Zhou
2022-03-22 12:59 ` Peter Zijlstra [this message]
2022-03-22 13:38 ` [External] " Chengming Zhou
2022-03-22 14:54 ` Peter Zijlstra
2022-03-22 15:16 ` Chengming Zhou
2022-03-22 15:28 ` Chengming Zhou
2022-03-22 22:06 ` Namhyung Kim
2022-03-23 8:11 ` Peter Zijlstra
2022-03-22 12:08 ` [PATCH v2 2/6] perf/core: Introduce percpu perf_cgroup Chengming Zhou
2022-03-22 13:01 ` Peter Zijlstra
2022-03-22 16:33 ` [External] " Chengming Zhou
2022-03-23 8:13 ` Peter Zijlstra
2022-03-23 12:58 ` Chengming Zhou
2022-03-22 22:21 ` Namhyung Kim
2022-03-22 22:18 ` Namhyung Kim
2022-03-23 1:27 ` [Phishing Risk] [External] " Chengming Zhou
2022-03-23 12:51 ` Peter Zijlstra
2022-03-23 13:07 ` [External] " Chengming Zhou
2022-03-23 13:17 ` Peter Zijlstra
2022-03-23 13:37 ` Chengming Zhou
2022-03-23 14:05 ` Peter Zijlstra
2022-03-23 15:44 ` Chengming Zhou
2022-03-22 12:08 ` [PATCH v2 3/6] perf/core: Don't pass task around when ctx sched in Chengming Zhou
2022-03-22 13:01 ` Peter Zijlstra
2022-03-22 12:08 ` [PATCH v2 4/6] perf/core: Use stable cpuctx->cgrp when update perf cgroup time Chengming Zhou
2022-03-22 13:03 ` Peter Zijlstra
2022-03-22 12:08 ` [PATCH v2 5/6] perf/core: Always set cpuctx cgrp when enable cgroup event Chengming Zhou
2022-03-22 12:08 ` [PATCH v2 6/6] perf/core: Don't need event_filter_match when merge_sched_in() Chengming Zhou
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