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xen-devel
[Xen-devel] Re: [PATCH 06/13] x86/ticketlock: add slowpath logic
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To: |
Eric Northup <digitaleric@xxxxxxxxxx> |
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Subject: |
[Xen-devel] Re: [PATCH 06/13] x86/ticketlock: add slowpath logic |
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From: |
Jeremy Fitzhardinge <jeremy@xxxxxxxx> |
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Date: |
Fri, 02 Sep 2011 12:32:25 -0700 |
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Cc: |
Marcelo Tosatti <mtosatti@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>, Andi Kleen <andi@xxxxxxxxxxxxxx>, Avi Kivity <avi@xxxxxxxxxx>, Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>, "H. Peter Anvin" <hpa@xxxxxxxxx>, Ingo Molnar <mingo@xxxxxxx>, Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>, Xen Devel <xen-devel@xxxxxxxxxxxxxxxxxxx> |
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Fri, 02 Sep 2011 12:33:01 -0700 |
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<cover.1314922370.git.jeremy.fitzhardinge@xxxxxxxxxx> <8a788f3fbf2ad1316e462bf5aae623bab9d38319.1314922370.git.jeremy.fitzhardinge@xxxxxxxxxx> <CAG7+5M0s76O_TWBaoY2KU+WeEoJYEhkLLDXfg81WHYNvavH3yw@xxxxxxxxxxxxxx> |
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On 09/02/2011 11:46 AM, Eric Northup wrote:
> On Thu, Sep 1, 2011 at 5:54 PM, Jeremy Fitzhardinge <jeremy@xxxxxxxx> wrote:
>> From: Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>
>>
>> Maintain a flag in both LSBs of the ticket lock which indicates whether
>> anyone is in the lock slowpath and may need kicking when the current
>> holder unlocks. The flags are set when the first locker enters
>> the slowpath, and cleared when unlocking to an empty queue.
> Are there actually two flags maintained? I only see the one in the
> ticket tail getting set/cleared/tested.
Yeah, there's only one flag, so there's a spare bit in the other half.
j
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