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

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Message-ID: <20250604070608.GF38114@noisy.programming.kicks-ass.net>
Date: Wed, 4 Jun 2025 09:06:08 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Yeoreum Yun <yeoreum.yun@....com>
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

On Tue, Jun 03, 2025 at 04:17:04PM +0100, Yeoreum Yun wrote:
> 
> 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()")

Right. But lets just get the patch for the current tree right. Then we
can worry about backports :-)