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SubjectRe: [PATCH 03/20] x86/ticketlock: Use C for __ticket_spin_unlock
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.

>+
>+}
> #else
>-# define UNLOCK_LOCK_PREFIX
>+static __always_inline void __ticket_unlock_release(struct arch_spinlock *lock)
>+{
>+ barrier();
>+ lock->tickets.head++;
>+ barrier();

The second barrier() is not needed.

Thanks.


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