x86, ticketlock: Make __ticket_spin_trylock common

Make trylock code common regardless of ticket size.

(Also, rename arch_spinlock.slock to head_tail.)

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Link: http://lkml.kernel.org/r/4E5BCC40.3030501@goop.org
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

1 files changed, 12 insertions, 39 deletions

diff --git a/arch/x86/include/asm/spinlock.h b/arch/x86/include/asm/spinlock.h
index b69e0b473de..f5695eeb83f 100644
--- a/arch/x86/include/asm/spinlock.h
+++ b/arch/x86/include/asm/spinlock.h
@@ -69,60 +69,33 @@ static __always_inline void __ticket_spin_lock(arch_spinlock_t *lock)
         barrier();              /* make sure nothing creeps before the lock is taken */
 }
 
-#if (NR_CPUS < 256)
 static __always_inline int __ticket_spin_trylock(arch_spinlock_t *lock)
 {
-        unsigned int tmp, new;
-
-        asm volatile("movzwl %2, %0\n\t"
-                     "cmpb %h0,%b0\n\t"
-                     "leal 0x100(%" REG_PTR_MODE "0), %1\n\t"
-                     "jne 1f\n\t"
-                     LOCK_PREFIX "cmpxchgw %w1,%2\n\t"
-                     "1:"
-                     "sete %b1\n\t"
-                     "movzbl %b1,%0\n\t"
-                     : "=&a" (tmp), "=&q" (new), "+m" (lock->slock)
-                     :
-                     : "memory", "cc");
+        arch_spinlock_t old, new;
+
+        old.tickets = ACCESS_ONCE(lock->tickets);
+        if (old.tickets.head != old.tickets.tail)
+                return 0;
 
-        return tmp;
+        new.head_tail = old.head_tail + (1 << TICKET_SHIFT);
+
+        /* cmpxchg is a full barrier, so nothing can move before it */
+        return cmpxchg(&lock->head_tail, old.head_tail, new.head_tail) == old.head_tail;
 }
 
+#if (NR_CPUS < 256)
 static __always_inline void __ticket_spin_unlock(arch_spinlock_t *lock)
 {
         asm volatile(UNLOCK_LOCK_PREFIX "incb %0"
-                     : "+m" (lock->slock)
+                     : "+m" (lock->head_tail)
                      :
                      : "memory", "cc");
 }
 #else
-static __always_inline int __ticket_spin_trylock(arch_spinlock_t *lock)
-{
-        unsigned tmp;
-        unsigned new;
-
-        asm volatile("movl %2,%0\n\t"
-                     "movl %0,%1\n\t"
-                     "roll $16, %0\n\t"
-                     "cmpl %0,%1\n\t"
-                     "leal 0x00010000(%" REG_PTR_MODE "0), %1\n\t"
-                     "jne 1f\n\t"
-                     LOCK_PREFIX "cmpxchgl %1,%2\n\t"
-                     "1:"
-                     "sete %b1\n\t"
-                     "movzbl %b1,%0\n\t"
-                     : "=&a" (tmp), "=&q" (new), "+m" (lock->slock)
-                     :
-                     : "memory", "cc");
-
-        return tmp;
-}
-
 static __always_inline void __ticket_spin_unlock(arch_spinlock_t *lock)
 {
         asm volatile(UNLOCK_LOCK_PREFIX "incw %0"
-                     : "+m" (lock->slock)
+                     : "+m" (lock->head_tail)
                      :
                      : "memory", "cc");
 }