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

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Message-ID: <aD8R8Bke1KZifJDH@e129823.arm.com>
Date: Tue, 3 Jun 2025 16:17:04 +0100
From: Yeoreum Yun <yeoreum.yun@....com>
To: Peter Zijlstra <peterz@...radead.org>
Cc: Leo Yan <leo.yan@....com>, mingo@...hat.com, mingo@...nel.org,
	acme@...nel.org, namhyung@...nel.org, 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, David Wang <00107082@....com>
Subject: Re: [PATCH 1/1] perf/core: fix dangling cgroup pointer in cpuctx


Hi Peter,

>
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -2120,18 +2120,6 @@ list_del_event(struct perf_event *event,
>  	if (event->group_leader == event)
>  		del_event_from_groups(event, ctx);
>
> -	/*
> -	 * If event was in error state, then keep it
> -	 * that way, otherwise bogus counts will be
> -	 * returned on read(). The only way to get out
> -	 * of error state is by explicit re-enabling
> -	 * of the event
> -	 */
> -	if (event->state > PERF_EVENT_STATE_OFF) {
> -		perf_cgroup_event_disable(event, ctx);
> -		perf_event_set_state(event, PERF_EVENT_STATE_OFF);
> -	}
> -
>  	ctx->generation++;
>  	event->pmu_ctx->nr_events--;

JFYI, this removal should be not included when you backport to v6.15
unless your patch backport together:
  commit 90661365021a ("perf Unify perf_event_free_task() / perf_evenet_exit_task_context()")

Thanks.

--
Sincerely,
Yeoreum Yun