Date: Wed, 22 Oct 2014 18:37:43 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Oleg Nesterov <oleg@redhat.com>
Cc: Kirill Tkhai <tkhai@yandex.ru>, Kirill Tkhai <ktkhai@parallels.com>,
        linux-kernel@vger.kernel.org, Ingo Molnar <mingo@redhat.com>,
        Vladimir Davydov <vdavydov@parallels.com>, cl@linux.com
Subject: Re: [PATCH v3] sched/numa: fix unsafe get_task_struct() in
 task_numa_assign()
Message-ID: <20141022163743.GI21513@worktop.programming.kicks-ass.net>
References: <1413800145.19914.23.camel@tkhai>
 <20141020144757.GA10939@redhat.com>
 <20141020165614.GA16373@redhat.com>
 <20141020182748.GA20424@redhat.com>
 <54456E26.2000103@yandex.ru>
 <20141020205006.GA2500@redhat.com>
 <20141021094558.GQ23531@worktop.programming.kicks-ass.net>
 <20141021190335.GA12851@redhat.com>
 <20141022090954.GF12706@worktop.programming.kicks-ass.net>
 <20141022161450.GA27607@redhat.com>
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On Wed, Oct 22, 2014 at 06:14:50PM +0200, Oleg Nesterov wrote:
> Hmm. so perhaps I misunderstood your concern...
> 
> Do you mean that on !x86 a plain LOAD can "corrupt" the memory as it seen
> from another vaddr?

I'm not sure. Stores for sure, loads I'm not sure about.

I suspect loads are OK, the aliasing cacheline will be !modified and
therefore later eviction should discard (not write back). But like said,
I'm not at all sure.

I would hesitate to put such assumptions into generic code -- although
it appears we already have.
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