linux-kernel - Re: [PATCH v9 3/3] trace,x86: code-sharing between non-trace and trace irq handlers

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Date:	Fri, 15 Feb 2013 16:13:31 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Seiji Aguchi <seiji.aguchi@....com>
CC:	Steven Rostedt <rostedt@...dmis.org>,
	"x86@...nel.org" <x86@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Thomas Gleixner (tglx@...utronix.de)" <tglx@...utronix.de>,
	"'mingo@...e.hu' (mingo@...e.hu)" <mingo@...e.hu>,
	"Borislav Petkov (bp@...en8.de)" <bp@...en8.de>,
	Satoru Moriya <satoru.moriya@....com>,
	"dle-develop@...ts.sourceforge.net" 
	<dle-develop@...ts.sourceforge.net>,
	"linux-edac@...r.kernel.org" <linux-edac@...r.kernel.org>,
	"Luck, Tony (tony.luck@...el.com)" <tony.luck@...el.com>
Subject: Re: [PATCH v9 3/3] trace,x86: code-sharing between non-trace and
 trace irq handlers

On 02/04/2013 02:50 PM, Seiji Aguchi wrote:
> [Issue]
> 
> Currently, irq vector handlers for tracing are just
> copied non-trace handlers by simply inserting tracepoints.
> 
> It is difficult to manage the codes.
> 
> [Solution]
> 
> This patch shares common codes between non-trace and trace handlers
> as follows to make them manageable and readable.
> 
> Non-trace irq handler:
> smp_irq_handler()
> {
> 	entering_irq(); /* pre-processing of this handler */
> 	__smp_irq_handler(); /*
>                           * common logic between non-trace and trace handlers
>                           * in a vector.
>                           */
> 	exiting_irq(); /* post-processing of this handler */
> 
> }
> 
> Trace irq_handler:
> smp_trace_irq_handler()
> {
> 	entering_irq(); /* pre-processing of this handler */
> 	trace_irq_entry(); /* tracepoint for irq entry */
> 	__smp_irq_handler(); /*
>                           * common logic between non-trace and trace handlers
>                           * in a vector.
>                           */
> 	trace_irq_exit(); /* tracepoint for irq exit */
> 	exiting_irq(); /* post-processing of this handler */
> 
> }
> 

How important is it that the tracepoint is *inside* the enter/exit
handling?  If not, it would be simpler to just do:

smp_trace_irq_handler()
{
	trace_irq_entry();
	smp_irq_handler();
	trace_irq_exit();
}

... which seems a bit cleaner.  If this isn't possible, then this patch
is fine, but please add to the patch description why the simple wrapper
isn't doable.

	-hpa


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