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xen-devel
Re: [Xen-devel] [PATCH 00/10] [PATCH RFC V2] Paravirtualized ticketlocks
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To: |
Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> |
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Subject: |
Re: [Xen-devel] [PATCH 00/10] [PATCH RFC V2] Paravirtualized ticketlocks |
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From: |
Jeremy Fitzhardinge <jeremy@xxxxxxxx> |
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Date: |
Wed, 28 Sep 2011 12:06:36 -0700 |
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Cc: |
Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>, Nick Piggin <npiggin@xxxxxxxxx>, KVM <kvm@xxxxxxxxxxxxxxx>, Peter Zijlstra <peterz@xxxxxxxxxxxxx>, the arch/x86 maintainers <x86@xxxxxxxxxx>, Linux Kernel Mailing List <linux-kernel@xxxxxxxxxxxxxxx>, Marcelo Tosatti <mtosatti@xxxxxxxxxx>, Andi Kleen <andi@xxxxxxxxxxxxxx>, Avi Kivity <avi@xxxxxxxxxx>, Jan Beulich <JBeulich@xxxxxxxx>, "H. Peter Anvin" <hpa@xxxxxxxxx>, Ingo Molnar <mingo@xxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>, Stephan Diestelhorst <stephan.diestelhorst@xxxxxxx> |
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Wed, 28 Sep 2011 12:07:57 -0700 |
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<cover.1315878463.git.jeremy.fitzhardinge@xxxxxxxxxx> <4E835851.7070502@xxxxxxxxx> <4E835E50.2020307@xxxxxxxx> <201109282008.17722.stephan.diestelhorst@xxxxxxx> <CA+55aFwm7ESNfrHhEHrAKcjcPUq8YxtuEkJd5PzAekYo2dMYNw@xxxxxxxxxxxxxx> |
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On 09/28/2011 11:49 AM, Linus Torvalds wrote:
> But I don't care all *that* deeply. I do agree that the xaddw trick is
> pretty tricky. I just happen to think that it's actually *less* tricky
> than "read the upper bits separately and depend on subtle ordering
> issues with another writer that happens at the same time on another
> CPU".
>
> So I can live with either form - as long as it works. I think it might
> be easier to argue that the xaddw is guaranteed to work, because all
> values at all points are unarguably atomic (yeah, we read the lower
> bits nonatomically, but as the owner of the lock we know that nobody
> else can write them).
Exactly. I just did a locked add variant, and while the code looks a
little simpler, it definitely has more actual complexity to analyze.
J
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- Re: [Xen-devel] [PATCH 00/10] [PATCH RFC V2] Paravirtualized ticketlocks, (continued)
- Re: [Xen-devel] [PATCH 00/10] [PATCH RFC V2] Paravirtualized ticketlocks, Linus Torvalds
- Re: [Xen-devel] [PATCH 00/10] [PATCH RFC V2] Paravirtualized ticketlocks, Jan Beulich
- Re: [Xen-devel] [PATCH 00/10] [PATCH RFC V2] Paravirtualized ticketlocks, Linus Torvalds
- Re: [Xen-devel] [PATCH 00/10] [PATCH RFC V2] Paravirtualized ticketlocks, Jeremy Fitzhardinge
- Re: [Xen-devel] [PATCH 00/10] [PATCH RFC V2] Paravirtualized ticketlocks, Linus Torvalds
- Re: [Xen-devel] [PATCH 00/10] [PATCH RFC V2] Paravirtualized ticketlocks, H. Peter Anvin
- Re: [Xen-devel] [PATCH 00/10] [PATCH RFC V2] Paravirtualized ticketlocks, Jeremy Fitzhardinge
- Re: [Xen-devel] [PATCH 00/10] [PATCH RFC V2] Paravirtualized ticketlocks, Stephan Diestelhorst
- Re: [Xen-devel] [PATCH 00/10] [PATCH RFC V2] Paravirtualized ticketlocks, Jeremy Fitzhardinge
- Re: [Xen-devel] [PATCH 00/10] [PATCH RFC V2] Paravirtualized ticketlocks, Linus Torvalds
- Re: [Xen-devel] [PATCH 00/10] [PATCH RFC V2] Paravirtualized ticketlocks,
Jeremy Fitzhardinge <=
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