linux-kernel - Re: [Dle-develop] [PATCH -tip v3 3/5] x86: Introduce text_poke_smp

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Message-ID: <4C189868.8050900@hitachi.com>
Date:	Wed, 16 Jun 2010 18:24:56 +0900
From:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To:	Frederic Weisbecker <fweisbec@...il.com>
Cc:	DLE <dle-develop@...ts.sourceforge.net>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Jason Baron <jbaron@...hat.com>,
	lkml <linux-kernel@...r.kernel.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Ingo Molnar <mingo@...e.hu>, 2nddept-manager@....hitachi.co.jp
Subject: Re: [Dle-develop] [PATCH -tip v3 3/5] x86: Introduce	text_poke_smp_batch()
 for	batch-code modifying

Frederic Weisbecker wrote:
> On Wed, May 19, 2010 at 12:53:26PM -0400, Masami Hiramatsu wrote:
>> Introduce text_poke_smp_batch(). This function modifies several
>> text areas with one stop_machine() on SMPr. Because calling
>> stop_machine() is heavy task, it is better to aggregate text_poke
>> requests.
>>
>> Signed-off-by: Masami Hiramatsu <mhiramat@...hat.com>
>> Cc: Ananth N Mavinakayanahalli <ananth@...ibm.com>
>> Cc: Ingo Molnar <mingo@...e.hu>
>> Cc: Jim Keniston <jkenisto@...ibm.com>
>> Cc: Jason Baron <jbaron@...hat.com>
>> Cc: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
> <snip>
>> +/**
>> + * text_poke_smp_batch - Update instructions on a live kernel on SMP
>> + * @params: an array of text_poke parameters
>> + * @n: the number of elements in params.
>> + *
>> + * Modify multi-byte instruction by using stop_machine() on SMP. Since the
>> + * stop_machine() is heavy task, it is better to aggregate text_poke requests
>> + * and do it once if possible.
>> + *
>> + * Note: Must be called under get_online_cpus() and text_mutex.
>> + */
>> +void __kprobes text_poke_smp_batch(struct text_poke_param *params, int n)
>> +{
>> +	struct text_poke_params tpp = {.params = params, .nparams = n};
>> +
>> +	atomic_set(&stop_machine_first, 1);
>> +	wrote_text = 0;
>> +	stop_machine(stop_machine_text_poke, (void *)&tpp, NULL);
>> +}
> 
> 
> Looks good. But wouldn't it be even better to get stop_machine()
> be able to support batches itself?
> 
> We could have stop_machine_queue() and stop_machine_flush(),
> stop_machine() would be a shortcut for both, to execute single jobs,
> may be that could simplify some code here and there.
> 

Ah, that's nice too :) But I don't know other people who need
that interfaces. Would you know there are any other potential users?

Thank you,
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