Message-ID: <54D8AD85.1070409@linux.vnet.ibm.com>
Date: Mon, 09 Feb 2015 18:22:21 +0530
From: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
Organization: IBM
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To: Peter Zijlstra <peterz@infradead.org>
CC: Jeremy Fitzhardinge <jeremy@goop.org>, tglx@linutronix.de,
        mingo@redhat.com, hpa@zytor.com, torvalds@linux-foundation.org,
        konrad.wilk@oracle.com, pbonzini@redhat.com,
        paulmck@linux.vnet.ibm.com, waiman.long@hp.com, davej@redhat.com,
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        ak@linux.intel.com, jasowang@redhat.com, linux-kernel@vger.kernel.org,
        kvm@vger.kernel.org, virtualization@lists.linux-foundation.org,
        xen-devel@lists.xenproject.org, riel@redhat.com,
        borntraeger@de.ibm.com, akpm@linux-foundation.org,
        a.ryabinin@samsung.com, sasha.levin@oracle.com
Subject: Re: [PATCH] x86 spinlock: Fix memory corruption on completing completions
References: <1423234148-13886-1-git-send-email-raghavendra.kt@linux.vnet.ibm.com> <54D7D19B.1000103@goop.org> <54D87F1E.9060307@linux.vnet.ibm.com> <20150209120227.GT21418@twins.programming.kicks-ass.net>
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On 02/09/2015 05:32 PM, Peter Zijlstra wrote:
> On Mon, Feb 09, 2015 at 03:04:22PM +0530, Raghavendra K T wrote:
>> So we have 3 choices,
>> 1. xadd
>> 2. continue with current approach.
>> 3. a read before unlock and also after that.
>
> For the truly paranoid we have probe_kernel_address(), suppose the lock
> was in module space and the module just got unloaded under us.
>

Thanks.. Good idea, How costly is it?
atleast we could do probe_kernel_address() and check the value of
slowpath flag if people as us to address invalid read problem.

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