Re: [PATCH 01/12] perf: Use tracepoint_synchronize_unregister() to flush any pending tracepoint call

[Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>]

* Frederic Weisbecker (fweisbec@gmail.com) wrote:
> We use synchronize_sched() to ensure a tracepoint won't be called
> while/after we release the perf buffers it references.
> 
> But the tracepoint API has its own API for that:
> tracepoint_synchronize_unregister(). Use it instead as it's
> self-explanatory and eases maintainance.
> 
> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>

Acked-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Thanks!

Mathieu

> Cc: Ingo Molnar <mingo@elte.hu>
> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
> Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
> Cc: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
> Cc: Steven Rostedt <rostedt@goodmis.org>
> Cc: Li Zefan <lizf@cn.fujitsu.com>
> ---
>  kernel/trace/trace_event_perf.c |    6 +++---
>  1 files changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/kernel/trace/trace_event_perf.c b/kernel/trace/trace_event_perf.c
> index 2375165..000e6e8 100644
> --- a/kernel/trace/trace_event_perf.c
> +++ b/kernel/trace/trace_event_perf.c
> @@ -131,10 +131,10 @@ void perf_trace_destroy(struct perf_event *p_event)
>  	tp_event->class->reg(tp_event, TRACE_REG_PERF_UNREGISTER);
>  
>  	/*
> -	 * Ensure our callback won't be called anymore. See
> -	 * tracepoint_probe_unregister() and __DO_TRACE().
> +	 * Ensure our callback won't be called anymore. The buffers
> +	 * will be freed after that.
>  	 */
> -	synchronize_sched();
> +	tracepoint_synchronize_unregister();
>  
>  	free_percpu(tp_event->perf_events);
>  	tp_event->perf_events = NULL;
> -- 
> 1.6.2.3
> 

-- 
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com