linux-kernel - Re: [PATCH 1/1] perf/core: fix dangling cgroup pointer in cpuctx

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Message-ID: <5238de9d.6895.1973492091b.Coremail.00107082@163.com>
Date: Tue, 3 Jun 2025 14:54:35 +0800 (CST)
From: "David Wang" <00107082@....com>
To: "Yeoreum Yun" <yeoreum.yun@....com>
Cc: peterz@...radead.org, mingo@...hat.com, mingo@...nel.org,
	acme@...nel.org, namhyung@...nel.org, leo.yan@....com,
	mark.rutland@....com, alexander.shishkin@...ux.intel.com,
	jolsa@...nel.org, irogers@...gle.com, adrian.hunter@...el.com,
	kan.liang@...ux.intel.com, linux-perf-users@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] perf/core: fix dangling cgroup pointer in cpuctx


At 2025-06-03 14:34:59, "Yeoreum Yun" <yeoreum.yun@....com> wrote:
>Hi David,
>> > attach_state doesn't related for event->state change.
>> > if one event already cleared PERF_ATTACH_CONTEXT, that event is called
>> > via list_del_event()
>>
>> Maybe this concern could be clarified, what about other subtle impacts.
>> The change should be thorough reviewed, if you want to push it further.
>>
>> It takes me more than a month to figure out a procedure to reproduce the kernel panic bug,
>> It is  just very hard to capture a bug happens in rare situation.
>>
>> And your patch has a global impact, it changes behavior unnecessarily.
>
>TBH, this patch just change of time of "event->state" while doing,
>As my bad miss the disable cgorup perf.
>I think there seems no other side effect for chaning state while in
>removing event.
>But, Let's wait for other people's review.
>

The *risk* is unnecessary, we can confine the scope of DETACH_EXIT.
Why keep making global changes when confined changes are available?


David