linux-kernel - task_numa_fault() && TASK

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Message-ID: <20140903160819.GA7682@redhat.com>
Date:	Wed, 3 Sep 2014 18:08:19 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Peter Zijlstra <peterz@...radead.org>,
	Rik van Riel <riel@...hat.com>, Mel Gorman <mgorman@...e.de>
Cc:	Kautuk Consul <consul.kautuk@...il.com>,
	Ingo Molnar <mingo@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Michal Hocko <mhocko@...e.cz>,
	David Rientjes <rientjes@...gle.com>,
	Ionut Alexa <ionut.m.alexa@...il.com>,
	Guillaume Morin <guillaume@...infr.org>,
	linux-kernel@...r.kernel.org, Kirill Tkhai <tkhai@...dex.ru>
Subject: task_numa_fault() && TASK_DEAD

On 09/02, Oleg Nesterov wrote:
>
> The usage of TASK_DEAD in task_numa_fault() is wrong in any case.

Rik, I can't understand why task_numa_fault() needs this check at all,
but "if (p->state == TASK_DEAD)" looks certainly wrong. You could replace
this check with BUG_ON(p->state == TASK_DEAD). Perhaps you meant PF_EXITING?

And a stupid (really, I don't understand this code) question:

	/* for example, ksmd faulting in a user's mm */
	if (!p->mm)
		return;

OK, but perhaps it make sense to pass "mm" as another argument and do

	/* ksmd faulting in a user's mm, or debugger, or kthread use_mm() caller */
	if (p->mm != mm)
		return;

?

Oleg.

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