linux-kernel - Re: [PATCH v2 05/12] perf/x86: add cross-HT counter exclusion infrastructure

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Date:	Wed, 22 Oct 2014 19:25:40 +0200
From:	Stephane Eranian <eranian@...gle.com>
To:	Jiri Olsa <jolsa@...hat.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	"mingo@...e.hu" <mingo@...e.hu>,
	"ak@...ux.intel.com" <ak@...ux.intel.com>,
	"Liang, Kan" <kan.liang@...el.com>, Borislav Petkov <bp@...en8.de>,
	Maria Dimakopoulou <maria.n.dimakopoulou@...il.com>
Subject: Re: [PATCH v2 05/12] perf/x86: add cross-HT counter exclusion infrastructure

On Wed, Oct 22, 2014 at 5:07 PM, Jiri Olsa <jolsa@...hat.com> wrote:
> On Thu, Oct 09, 2014 at 06:34:39PM +0200, Stephane Eranian wrote:
>> From: Maria Dimakopoulou <maria.n.dimakopoulou@...il.com>
>>
>
> SNIP
>
>> +struct intel_excl_cntrs *allocate_excl_cntrs(int cpu)
>> +{
>> +     struct intel_excl_cntrs *c;
>> +     int i;
>> +
>> +     c = kzalloc_node(sizeof(struct intel_excl_cntrs),
>> +                      GFP_KERNEL, cpu_to_node(cpu));
>> +     if (c) {
>> +             spin_lock_init(&c->lock);
>> +             for (i = 0; i < X86_PMC_IDX_MAX; i++) {
>> +                     c->states[0].state[i] = INTEL_EXCL_UNUSED;
>> +                     c->states[0].init_state[i] = INTEL_EXCL_UNUSED;
>> +
>> +                     c->states[1].state[i] = INTEL_EXCL_UNUSED;
>> +                     c->states[1].init_state[i] = INTEL_EXCL_UNUSED;
>
> 'c' is allocated with kzalloc_node, seems there's no need
> to re-initialize states it to zero again with INTEL_EXCL_UNUSED
>
You are assuming that INTEL_EXCL_UNUSED=0 always.
That means it needs to be clear there is a dependency here.

I am happy removing that if someone confirms the assumption is common
in the kernel
for this kind of fields.


> jirka
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