linux-kernel - Re: [PATCH v2 5/6] trace: Add tracepoints to call function interrupt handlers

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Message-ID: <1311855462.2617.171.camel@laptop>
Date:	Thu, 28 Jul 2011 14:17:42 +0200
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Vaibhav Nagarnaik <vnagarnaik@...gle.com>
Cc:	Frederic Weisbecker <fweisbec@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Michael Rubin <mrubin@...gle.com>,
	David Sharp <dhsharp@...gle.com>, linux-kernel@...r.kernel.org,
	x86@...nel.org
Subject: Re: [PATCH v2 5/6] trace: Add tracepoints to call function
 interrupt handlers

On Wed, 2011-07-27 at 11:57 -0700, Vaibhav Nagarnaik wrote:
> @@ -172,6 +173,7 @@ void generic_smp_call_function_interrupt(void)
>         struct call_function_data *data;
>         int cpu = smp_processor_id();
>  
> +       trace_call_function_ipi_entry(0);
>         /*
>          * Shouldn't receive this interrupt on a cpu that is not yet online.
>          */
> @@ -239,7 +241,7 @@ void generic_smp_call_function_interrupt(void)
>  
>                 csd_unlock(&data->csd);
>         }
> -
> +       trace_call_function_ipi_exit(0);
>  }
>  
>  /*
> @@ -252,6 +254,7 @@ void generic_smp_call_function_single_interrupt(void)
>         unsigned int data_flags;
>         LIST_HEAD(list);
>  
> +       trace_call_function_single_ipi_entry(0);
>         /*
>          * Shouldn't receive this interrupt on a cpu that is not yet online.
>          */
> @@ -282,6 +285,7 @@ void generic_smp_call_function_single_interrupt(void)
>                 if (data_flags & CSD_FLAG_LOCK)
>                         csd_unlock(data);
>         }
> +       trace_call_function_single_ipi_exit(0);
>  } 

The problem with this is that some archs only have a single IPI and
multiplex all IPIs on top, in that case you're either nesting interrupt
tracepoints or missing a part.

I really think you're doing this at the wrong level.

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