linux-kernel - Re: [PATCH v2] mm: correctly synchronize rss-counters at exit/exec

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Message-ID: <4F84936A.1060708@openvz.org>
Date:	Wed, 11 Apr 2012 00:09:14 +0400
From:	Konstantin Khlebnikov <khlebnikov@...nvz.org>
To:	Oleg Nesterov <oleg@...hat.com>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Hugh Dickins <hughd@...gle.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	Markus Trippelsdorf <markus@...ppelsdorf.de>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Subject: Re: [PATCH v2] mm: correctly synchronize rss-counters at exit/exec

Oleg Nesterov wrote:
> On 04/10, Konstantin Khlebnikov wrote:
>>
>> This patch moves sync_mm_rss() into mm_release(), and moves mm_release() out of
>> do_exit() and calls it earlier. After mm_release() there should be no page-faults.
>
> Can't prove, but I feel there should be a simpler fix...
>
> Anyway, this patch is not exactly correct.
>
>> @@ -959,9 +959,10 @@ void do_exit(long code)
>>   				preempt_count());
>>
>>   	acct_update_integrals(tsk);
>> -	/* sync mm's RSS info before statistics gathering */
>> -	if (tsk->mm)
>> -		sync_mm_rss(tsk->mm);
>> +
>> +	/* Release mm and sync mm's RSS info before statistics gathering */
>> +	mm_release(tsk, tsk->mm);
>
> This breaks kthread_stop() at least.
>
> The exiting kthread shouldn't do complete_vfork_done() until it
> sets ->exit_code.

Ouch, I was afraid something like that.

>
> Oleg.
>

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