linux-kernel - Re: [PATCH -tip 1/5] [CLEANUP] kprobes: Remove redundant text

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Date:	Tue, 11 May 2010 08:35:50 -0400
From:	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To:	Masami Hiramatsu <mhiramat@...hat.com>
Cc:	Ingo Molnar <mingo@...e.hu>, lkml <linux-kernel@...r.kernel.org>,
	systemtap <systemtap@...rces.redhat.com>,
	DLE <dle-develop@...ts.sourceforge.net>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Jim Keniston <jkenisto@...ibm.com>,
	Jason Baron <jbaron@...hat.com>
Subject: Re: [PATCH -tip 1/5] [CLEANUP] kprobes: Remove redundant
	text_mutex lock in optimize

* Masami Hiramatsu (mhiramat@...hat.com) wrote:
> Remove text_mutex locking in optimize_all_kprobes, because
> that function doesn't modify text but just order optimization
> to worker.

Hi Masami,

A few comments:

1) optimize_all_kprobes/unoptimize_all_kprobes should have comments saying that
they are always called with kprobe_mutex held.

2) The sentence above in the changelog could be changed into:

 ..."because this function doesn't modify text. It simply queues optimizations
for the kprobe_optimizer worker thread."

3)

static DEFINE_MUTEX(kprobe_mutex);      /* Protects kprobe_table */

.. should also state that it protects optimizing_list.

Thanks,

Mathieu

> 
> 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>
> ---
> 
>  kernel/kprobes.c |    2 --
>  1 files changed, 0 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/kprobes.c b/kernel/kprobes.c
> index 282035f..1d34eef 100644
> --- a/kernel/kprobes.c
> +++ b/kernel/kprobes.c
> @@ -606,14 +606,12 @@ static void __kprobes optimize_all_kprobes(void)
>  		return;
>  
>  	kprobes_allow_optimization = true;
> -	mutex_lock(&text_mutex);
>  	for (i = 0; i < KPROBE_TABLE_SIZE; i++) {
>  		head = &kprobe_table[i];
>  		hlist_for_each_entry_rcu(p, node, head, hlist)
>  			if (!kprobe_disabled(p))
>  				optimize_kprobe(p);
>  	}
> -	mutex_unlock(&text_mutex);
>  	printk(KERN_INFO "Kprobes globally optimized\n");
>  }
>  
> 
> 
> -- 
> Masami Hiramatsu
> e-mail: mhiramat@...hat.com

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