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xen-devel
[Xen-devel] Re: [PATCH 03/20] x86/ticketlock: Use C for __ticket_spin_un
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To: |
Jeremy Fitzhardinge <jeremy@xxxxxxxx> |
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Subject: |
[Xen-devel] Re: [PATCH 03/20] x86/ticketlock: Use C for __ticket_spin_unlock |
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From: |
Eric Dumazet <eric.dumazet@xxxxxxxxx> |
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Date: |
Wed, 03 Nov 2010 16:13:38 +0100 |
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Cc: |
Nick Piggin <npiggin@xxxxxxx>, Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>, Peter Zijlstra <peterz@xxxxxxxxxxxxx>, Srivatsa, Linux, Linux Kernel Mailing List <linux-kernel@xxxxxxxxxxxxxxx>, Jan Beulich <JBeulich@xxxxxxxxxx>, Virtualization <virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx>, Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>, Vaddagiri <vatsa@xxxxxxxxxxxxxxxxxx>, Avi Kivity <avi@xxxxxxxxxx>, "H. Peter Anvin" <hpa@xxxxxxxxx> |
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Wed, 03 Nov 2010 08:28:34 -0700 |
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Le mercredi 03 novembre 2010 à 10:59 -0400, Jeremy Fitzhardinge a
écrit :
> From: Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>
>
> If we don't need to use a locked inc for unlock, then implement it in C.
>
> Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>
> ---
> arch/x86/include/asm/spinlock.h | 33 ++++++++++++++++++---------------
> 1 files changed, 18 insertions(+), 15 deletions(-)
>
> diff --git a/arch/x86/include/asm/spinlock.h b/arch/x86/include/asm/spinlock.h
> index 6711d36..082990a 100644
> --- a/arch/x86/include/asm/spinlock.h
> +++ b/arch/x86/include/asm/spinlock.h
> @@ -33,9 +33,23 @@
> * On PPro SMP or if we are using OOSTORE, we use a locked operation to
> unlock
> * (PPro errata 66, 92)
> */
> -# define UNLOCK_LOCK_PREFIX LOCK_PREFIX
> +static __always_inline void __ticket_unlock_release(struct arch_spinlock
> *lock)
> +{
> + if (sizeof(lock->tickets.head) == sizeof(u8))
> + asm (LOCK_PREFIX "incb %0"
> + : "+m" (lock->tickets.head) : : "memory");
> + else
> + asm (LOCK_PREFIX "incw %0"
> + : "+m" (lock->tickets.head) : : "memory");
> +
> +}
> #else
> -# define UNLOCK_LOCK_PREFIX
> +static __always_inline void __ticket_unlock_release(struct arch_spinlock
> *lock)
> +{
> + barrier();
technically speaking, it should be : smp_wmb()
> + lock->tickets.head++;
> + barrier();
Not sure you need this one.
> +}
> #endif
>
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