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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.

  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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