[IA64] SMT friendly version of spin_unlock_wait()

We can be kinder to SMT systems in spin_unlock_wait.

Signed-off-by: Tony Luck <tony.luck@intel.com>

1 files changed, 15 insertions, 2 deletions

diff --git a/arch/ia64/include/asm/spinlock.h b/arch/ia64/include/asm/spinlock.h
index 4fa502739d64..239ecdc9516d 100644
--- a/arch/ia64/include/asm/spinlock.h
+++ b/arch/ia64/include/asm/spinlock.h
@@ -75,6 +75,20 @@ static __always_inline void __ticket_spin_unlock(raw_spinlock_t *lock)
         ACCESS_ONCE(*p) = (tmp + 2) & ~1;
 }
 
+static __always_inline void __ticket_spin_unlock_wait(raw_spinlock_t *lock)
+{
+        int     *p = (int *)&lock->lock, ticket;
+
+        ia64_invala();
+
+        for (;;) {
+                asm volatile ("ld4.c.nc %0=[%1]" : "=r"(ticket) : "r"(p) : "memory");
+                if (!(((ticket >> TICKET_SHIFT) ^ ticket) & TICKET_MASK))
+                        return;
+                cpu_relax();
+        }
+}
+
 static inline int __ticket_spin_is_locked(raw_spinlock_t *lock)
 {
         long tmp = ACCESS_ONCE(lock->lock);
@@ -123,8 +137,7 @@ static __always_inline void __raw_spin_lock_flags(raw_spinlock_t *lock,
 
 static inline void __raw_spin_unlock_wait(raw_spinlock_t *lock)
 {
-        while (__raw_spin_is_locked(lock))
-                cpu_relax();
+        __ticket_spin_unlock_wait(lock);
 }
 
 #define __raw_read_can_lock(rw)         (*(volatile int *)(rw) >= 0)