linux-kernel - Re: [tip:perf/core] jump label: x86 support

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Date:	Mon, 18 Oct 2010 08:48:28 -0400
From:	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	mingo@...hat.com, hpa@...or.com, linux-kernel@...r.kernel.org,
	rostedt@...dmis.org, tglx@...utronix.de, jbaron@...hat.com,
	linux-tip-commits@...r.kernel.org
Subject: Re: [tip:perf/core] jump label: x86 support

* Peter Zijlstra (peterz@...radead.org) wrote:
> On Fri, 2010-09-24 at 09:01 +0000, tip-bot for Jason Baron wrote:
> > +void arch_jump_label_transform(struct jump_entry *entry,
> > +                              enum jump_label_type type)
> > +{
> > +       union jump_code_union code;
> > +
> > +       if (type == JUMP_LABEL_ENABLE) {
> > +               code.jump = 0xe9;
> > +               code.offset = entry->target -
> > +                               (entry->code + JUMP_LABEL_NOP_SIZE);
> > +       } else
> > +               memcpy(&code, ideal_nop5, JUMP_LABEL_NOP_SIZE);
> > +       get_online_cpus();
> > +       mutex_lock(&text_mutex);
> > +       text_poke_smp((void *)entry->code, &code, JUMP_LABEL_NOP_SIZE);
> > +       mutex_unlock(&text_mutex);
> > +       put_online_cpus();
> > +} 
> 
> hpa, mathieu, what's the status of stop_machine less text poking?
> Because the above basically means we have to disable architecture
> jump_label support for -rt.

hpa got an unofficial answer from Intel OTC, that states the stop_machine-less
text poking procedure is valid.

http://lkml.org/lkml/2010/1/12/300

We are still waiting for the "official" blessing though.

Thanks,

Mathieu

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