Message-ID: <1423251764.1057.1.camel@stgolabs.net>
Subject: Re: [PATCH] x86 spinlock: Fix memory corruption on completing
 completions
From: Davidlohr Bueso <dave@stgolabs.net>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>,
        Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>,
        Peter Anvin <hpa@zytor.com>, Peter Zijlstra <peterz@infradead.org>,
        Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Paul McKenney <paulmck@linux.vnet.ibm.com>,
        Waiman Long <waiman.long@hp.com>, Dave Jones <davej@redhat.com>,
        Oleg Nesterov <oleg@redhat.com>,
        the arch/x86 maintainers <x86@kernel.org>,
        Jeremy Fitzhardinge <jeremy@goop.org>,
        Paul Gortmaker <paul.gortmaker@windriver.com>,
        Andi Kleen <ak@linux.intel.com>, Jason Wang <jasowang@redhat.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        KVM list <kvm@vger.kernel.org>,
        virtualization <virtualization@lists.linux-foundation.org>,
        xen-devel@lists.xenproject.org, Rik van Riel <riel@redhat.com>,
        Christian Borntraeger <borntraeger@de.ibm.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Andrey Ryabinin <a.ryabinin@samsung.com>,
        Sasha Levin <sasha.levin@oracle.com>
Date: Fri, 06 Feb 2015 11:42:44 -0800
In-Reply-To: <CA+55aFwZOgiUe5Zm=o24d6SshvoLbF1bq_VT0hdijR1hfoyi4A@mail.gmail.com>
References: <1423234148-13886-1-git-send-email-raghavendra.kt@linux.vnet.ibm.com>
	 <CA+55aFwZOgiUe5Zm=o24d6SshvoLbF1bq_VT0hdijR1hfoyi4A@mail.gmail.com>
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On Fri, 2015-02-06 at 08:25 -0800, Linus Torvalds wrote:
> On Fri, Feb 6, 2015 at 6:49 AM, Raghavendra K T
> <raghavendra.kt@linux.vnet.ibm.com> wrote:
> > Paravirt spinlock clears slowpath flag after doing unlock.
> [ fix edited out ]
> 
> So I'm not going to be applying this for 3.19, because it's much too
> late and the patch is too scary. Plus the bug probably effectively
> never shows up in real life (it is probably easy to trigger the
> speculative *read* but probably never the actual speculative write
> after dropping the lock last).
> 
> This will need a lot of testing by the paravirt people - both
> performance and correctness. So *maybe* for 3.20, but maybe for even
> later, and then marked for stable, of course.
> 
> Are there any good paravirt stress-tests that people could run for
> extended times?

locktorture inside a VM should give a proper pounding.

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