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: [External] Re: [PATCH v2 2/6] perf/core: Introduce percpu perf_cgroup
Date: Wed, 23 Mar 2022 09:13:58 +0100 [thread overview]
Message-ID: <YjrWxnnIZvn3PWoX@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <0a7ebd49-cfdd-911e-3982-44f594320b0f@bytedance.com>
On Wed, Mar 23, 2022 at 12:33:51AM +0800, Chengming Zhou wrote:
> On 2022/3/22 9:01 下午, Peter Zijlstra wrote:
> > On Tue, Mar 22, 2022 at 08:08:30PM +0800, Chengming Zhou wrote:
> >> Although we don't have incosistency problem any more, we can
> >> have other problem like:
> >>
> >> CPU1 CPU2
> >> (in context_switch) (attach running task)
> >> prev->cgroups = cgrp2
> >> perf_cgroup_sched_switch(prev, next)
> >> cgrp2 == cgrp2 is True
> >>
> >
> > Again, I'm not following, how can you attach to a running task from
> > another CPU ?
>
> Hi Peter, I make a little testcase which can reproduce the race
> problem, on system with PSI disabled. Because when PSI enabled,
> cgroup_move_task() will hold rq lock to assign task->cgroups.
No, the problem is that you're talking about cgroup attach while I'm
thinking of attaching a event to a task. And your picture has nothing to
clarify.
Those pictures of yours could really do with a few more function names
in them, otherwise it's absolutely unclear what code is running where.
next prev parent reply other threads:[~2022-03-23 8:14 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
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 [this message]
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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