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Subject[PATCH RFC 03/12] x86/ticketlock: Use C for __ticket_spin_unlock
If we don't need to use a locked inc for unlock, then implement it in C.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
---
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();
+ lock->tickets.head++;
+ barrier();
+}
#endif

/*
@@ -93,14 +107,6 @@ static __always_inline int __ticket_spin_trylock(arch_spinlock_t *lock)

return tmp;
}
-
-static __always_inline void __ticket_spin_unlock(arch_spinlock_t *lock)
-{
- asm volatile(UNLOCK_LOCK_PREFIX "incb %0"
- : "+m" (lock->slock)
- :
- : "memory", "cc");
-}
#else
static __always_inline void __ticket_spin_lock(arch_spinlock_t *lock)
{
@@ -144,15 +150,12 @@ static __always_inline int __ticket_spin_trylock(arch_spinlock_t *lock)

return tmp;
}
+#endif

static __always_inline void __ticket_spin_unlock(arch_spinlock_t *lock)
{
- asm volatile(UNLOCK_LOCK_PREFIX "incw %0"
- : "+m" (lock->slock)
- :
- : "memory", "cc");
+ __ticket_unlock_release(lock);
}
-#endif

static inline int __ticket_spin_is_locked(arch_spinlock_t *lock)
{
--
1.7.1.1



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