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[Xen-devel] Re: [PATCH 03/20] x86/ticketlock: Use C for __ticket_spin_unlock
- To: Américo Wang <xiyou.wangcong@xxxxxxxxx>
- From: Paolo Bonzini <pbonzini@xxxxxxxxxx>
- Date: Sat, 13 Nov 2010 23:34:06 +0100
- Cc: Nick Piggin <npiggin@xxxxxxx>, Jeremy Fitzhardinge <jeremy@xxxxxxxx>, 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>
- Delivery-date: Sat, 13 Nov 2010 14:35:07 -0800
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On 11/13/2010 11:05 AM, Américo Wang wrote:
On Wed, Nov 03, 2010 at 10:59:44AM -0400, Jeremy Fitzhardinge wrote:
* 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");
This 'if/else' really should be done with #ifdef, even though
the compiler may be smart enough to remove it.
That's a sure path to bitrot.
Paolo
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