linux-kernel - Re: [PATCH 3/4] perf cgroup: Clean up perf_cgroup

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Date:	Thu, 3 Mar 2011 09:37:33 +0100
From:	Stephane Eranian <eranian@...gle.com>
To:	Li Zefan <lizf@...fujitsu.com>
Cc:	Ingo Molnar <mingo@...e.hu>, Peter Zijlstra <peterz@...radead.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/4] perf cgroup: Clean up perf_cgroup_create()

Li,

I have to NACK this patch or at least request more information.

The for_each_possible_cpu() is initializing
what's allocated via alloc_percpu(), jc->info and NOT jc.

I don't think this gets zeroed by this allocator. But I could
be wrong.


On Thu, Mar 3, 2011 at 7:26 AM, Li Zefan <lizf@...fujitsu.com> wrote:
> - Use kzalloc() to replace kmalloc() + memset().
> - Remove redundant initialization, since alloc_percpu() returns
>  zero-filled percpu memory.
>
> Signed-off-by: Li Zefan <lizf@...fujitsu.com>
> ---
>  kernel/perf_event.c |   11 +----------
>  1 files changed, 1 insertions(+), 10 deletions(-)
>
> diff --git a/kernel/perf_event.c b/kernel/perf_event.c
> index dca92b2..d6b3d16 100644
> --- a/kernel/perf_event.c
> +++ b/kernel/perf_event.c
> @@ -7341,26 +7341,17 @@ static struct cgroup_subsys_state *perf_cgroup_create(
>        struct cgroup_subsys *ss, struct cgroup *cont)
>  {
>        struct perf_cgroup *jc;
> -       struct perf_cgroup_info *t;
> -       int c;
>
> -       jc = kmalloc(sizeof(*jc), GFP_KERNEL);
> +       jc = kzalloc(sizeof(*jc), GFP_KERNEL);
>        if (!jc)
>                return ERR_PTR(-ENOMEM);
>
> -       memset(jc, 0, sizeof(*jc));
> -
>        jc->info = alloc_percpu(struct perf_cgroup_info);
>        if (!jc->info) {
>                kfree(jc);
>                return ERR_PTR(-ENOMEM);
>        }
>
> -       for_each_possible_cpu(c) {
> -               t = per_cpu_ptr(jc->info, c);
> -               t->time = 0;
> -               t->timestamp = 0;
> -       }
>        return &jc->css;
>  }
>
> --
> 1.6.3
>
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