linux-kernel - Re: [PATCH v6 5/5] perf: Support deferred user callchains for per CPU events

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Message-ID: <aBPXpyd8HM6JrDPg@google.com>
Date: Thu, 1 May 2025 13:20:55 -0700
From: Namhyung Kim <namhyung@...nel.org>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org,
	Masami Hiramatsu <mhiramat@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Josh Poimboeuf <jpoimboe@...nel.org>, x86@...nel.org,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Indu Bhagat <indu.bhagat@...cle.com>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Jiri Olsa <jolsa@...nel.org>, Ian Rogers <irogers@...gle.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	linux-perf-users@...r.kernel.org, Mark Brown <broonie@...nel.org>,
	linux-toolchains@...r.kernel.org, Jordan Rome <jordalgo@...a.com>,
	Sam James <sam@...too.org>,
	Andrii Nakryiko <andrii.nakryiko@...il.com>,
	Jens Remus <jremus@...ux.ibm.com>,
	Florian Weimer <fweimer@...hat.com>,
	Andy Lutomirski <luto@...nel.org>, Weinan Liu <wnliu@...gle.com>,
	Blake Jones <blakejones@...gle.com>,
	Beau Belgrave <beaub@...ux.microsoft.com>,
	"Jose E. Marchesi" <jemarch@....org>,
	Alexander Aring <aahringo@...hat.com>
Subject: Re: [PATCH v6 5/5] perf: Support deferred user callchains for per
 CPU events

On Wed, Apr 30, 2025 at 09:32:07PM -0400, Steven Rostedt wrote:
> @@ -13100,13 +13269,20 @@ perf_event_alloc(struct perf_event_attr *attr, int cpu,
>  		}
>  	}
>  
> +	/* Setup unwind deferring for per CPU events */
> +	if (event->attr.defer_callchain && !task) {
> +		err = perf_add_unwind_deferred(event);
> +		if (err)
> +			return ERR_PTR(err);
> +	}
> +
>  	err = security_perf_event_alloc(event);
>  	if (err)
>  		return ERR_PTR(err);

It seems perf_remove_unwind_deferred() is not called from
__free_event() - with double underscores.

Thanks,
Namhyung


>  
>  	if (event->attr.defer_callchain)
>  		init_task_work(&event->pending_unwind_work,
> -			       perf_event_callchain_deferred);
> +			       perf_event_deferred_task);
>  
>  	/* symmetric to unaccount_event() in _free_event() */
>  	account_event(event);
> -- 
> 2.47.2
> 
>