linux-kernel - Re: [RFC][PATCH 2/3] perf: Take a hot regs snapshot for trace events

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Date:	Wed, 03 Mar 2010 11:06:27 -0500
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Frederic Weisbecker <fweisbec@...il.com>
Cc:	Ingo Molnar <mingo@...e.hu>, LKML <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Paul Mackerras <paulus@...ba.org>,
	Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: Re: [RFC][PATCH 2/3] perf: Take a hot regs snapshot for trace
 events

On Wed, 2010-03-03 at 07:55 +0100, Frederic Weisbecker wrote:

> +/*
>   * Output
>   */
>  static bool perf_output_space(struct perf_mmap_data *data, unsigned long tail,
> @@ -4337,6 +4347,8 @@ static const struct pmu perf_ops_task_clock = {
>  void perf_tp_event(int event_id, u64 addr, u64 count, void *record,
>  			  int entry_size)
>  {
> +	struct pt_regs regs;
> +
>  	struct perf_raw_record raw = {
>  		.size = entry_size,
>  		.data = record,
> @@ -4347,14 +4359,11 @@ void perf_tp_event(int event_id, u64 addr, u64 count, void *record,
>  		.raw = &raw,
>  	};
>  
> -	struct pt_regs *regs = get_irq_regs();
> -
> -	if (!regs)
> -		regs = task_pt_regs(current);
> +	PERF_SAVE_REGS(&regs);
>  
>  	/* Trace events already protected against recursion */
>  	do_perf_sw_event(PERF_TYPE_TRACEPOINT, event_id, count, 1,
> -				&data, regs);
> +				&data, &regs);

Off-topic: Why is the above a perf sw event? Couldn't that also be a
normal TRACE_EVENT()?

-- Steve

>  }
>  EXPORT_SYMBOL_GPL(perf_tp_event);
>  


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