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SubjectRE: Add memory barrier when waiting on futex
Date

> -----Original Message-----
> From: Peter Zijlstra [mailto:peterz@infradead.org]
> Sent: Tuesday, November 26, 2013 4:26 PM
> To: Ma, Xindong
> Cc: stable@vger.kernel.org; stable-commits@vger.kernel.org; Wysocki, Rafael
> J; ccross@google.com; tglx@linutronix.de; dvhart@linux.intel.com;
> mingo@kernel.org; linux-kernel@vger.kernel.org; gregkh@linuxfoundation.org;
> Tu, Xiaobing
> Subject: Re: Add memory barrier when waiting on futex
>
> On Tue, Nov 26, 2013 at 01:07:25AM +0000, Ma, Xindong wrote:
> > I've already aware that they've protected by spinlock, this is why I adding a
> memory barrier to fix it.
>
> That doesn't make sense.. the spinlocks should provide the required
> serialization, there's nothing to fix.
>
> > I reproduced this issue several times on android which running on IA dual
> core.
>
> I think you need to be more specific, in particular, if spinlocks do not provide
> serialization on your IA32 device, I'd call that thing broken.
> Adding random memory barriers is _WRONG_.
>
I agree with you. Thanks, Peter.


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