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Date: Wed, 3 Sep 2014 18:08:19 +0200
From: Oleg Nesterov <oleg@redhat.com>
To: Peter Zijlstra <peterz@infradead.org>, Rik van Riel <riel@redhat.com>,
        Mel Gorman <mgorman@suse.de>
Cc: Kautuk Consul <consul.kautuk@gmail.com>, Ingo Molnar <mingo@redhat.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Michal Hocko <mhocko@suse.cz>, David Rientjes <rientjes@google.com>,
        Ionut Alexa <ionut.m.alexa@gmail.com>,
        Guillaume Morin <guillaume@morinfr.org>, linux-kernel@vger.kernel.org,
        Kirill Tkhai <tkhai@yandex.ru>
Subject: task_numa_fault() && TASK_DEAD
Message-ID: <20140903160819.GA7682@redhat.com>
References: <1408964064-21447-1-git-send-email-consul.kautuk@gmail.com> <20140825155738.GA5944@redhat.com> <20140901153935.GQ27892@worktop.ger.corp.intel.com> <20140901175851.GA15210@redhat.com> <20140901190931.GD5806@worktop.ger.corp.intel.com> <20140902155208.GA28668@redhat.com> <20140902164714.GA17033@redhat.com>
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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.