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xen-devel
[Xen-devel] Re: [PATCH 06/20] x86/ticketlock: make __ticket_spin_trylock
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To: |
Jeremy Fitzhardinge <jeremy@xxxxxxxx> |
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Subject: |
[Xen-devel] Re: [PATCH 06/20] x86/ticketlock: make __ticket_spin_trylock common |
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From: |
Américo Wang <xiyou.wangcong@xxxxxxxxx> |
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Date: |
Sat, 13 Nov 2010 18:17:32 +0800 |
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Cc: |
Nick Piggin <npiggin@xxxxxxx>, Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>, Peter Zijlstra <peterz@xxxxxxxxxxxxx>, Srivatsa Vaddagiri <vatsa@xxxxxxxxxxxxxxxxxx>, Linux Kernel Mailing List <linux-kernel@xxxxxxxxxxxxxxx>, Jan Beulich <JBeulich@xxxxxxxxxx>, Linux Virtualization <virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx>, Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>, Avi Kivity <avi@xxxxxxxxxx>, "H. Peter Anvin" <hpa@xxxxxxxxx> |
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Delivery-date: |
Mon, 15 Nov 2010 01:22:47 -0800 |
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Mutt/1.5.19 (2009-01-05) |
On Wed, Nov 03, 2010 at 10:59:47AM -0400, Jeremy Fitzhardinge wrote:
>+ union {
>+ struct __raw_tickets tickets;
>+ __ticketpair_t slock;
>+ } tmp, new;
>+ int ret;
>+
>+ tmp.tickets = ACCESS_ONCE(lock->tickets);
>+ if (tmp.tickets.head != tmp.tickets.tail)
>+ return 0;
>+
>+ new.slock = tmp.slock + (1 << TICKET_SHIFT);
>+
>+ ret = cmpxchg(&lock->ticketpair, tmp.slock, new.slock) == tmp.slock;
>+ barrier(); /* just make nothing creeps before lock is
>claimed */
This one should be smp_wmb(), right? No CONFIG_X86_OOSTORE protected.
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