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

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Message-ID: <aD5+C41dsjvu9ZNP@e129823.arm.com>
Date: Tue, 3 Jun 2025 05:46:03 +0100
From: Yeoreum Yun <yeoreum.yun@....com>
To: 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
Cc: linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
	David Wang <00107082@....com>
Subject: Re: [PATCH 1/1] perf/core: fix dangling cgroup pointer in cpuctx

Hi Davia,

> I think this patch is no better than my patch in the original report
> https://lore.kernel.org/all/20250601173603.3920-1-00107082@163.com/
>
> This patch is more aggressive,  it add more changes to original logic, same practice
> as in the offending commit.  would raise more concerns about hidden side-effect.
>
> For example, this code  in list_del_event should raise concern about this patch
> 2099          * We can have double detach due to exit/hot-unplug + close.
>  2100          */
>  2101         if (!(event->attach_state & PERF_ATTACH_CONTEXT))
>  2102                 return;

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()

Also, your patch couldn't solve a problem describe in
commit a3c3c6667("perf/core: Fix child_total_time_enabled accounting bug at task exit")
for INCATIVE event's total_enable_time.

Thanks.

--
Sincerely,
Yeoreum Yun