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>

2 files changed, 16 insertions, 41 deletions

diff --git a/arch/x86/include/asm/spinlock.h b/arch/x86/include/asm/spinlock.h
index b69e0b473de6..f5695eeb83ff 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");
 }
diff --git a/arch/x86/include/asm/spinlock_types.h b/arch/x86/include/asm/spinlock_types.h
index 1c51bd231e49..8ebd5df7451e 100644
--- a/arch/x86/include/asm/spinlock_types.h
+++ b/arch/x86/include/asm/spinlock_types.h
@@ -9,8 +9,10 @@
 
 #if (CONFIG_NR_CPUS < 256)
 typedef u8  __ticket_t;
+typedef u16 __ticketpair_t;
 #else
 typedef u16 __ticket_t;
+typedef u32 __ticketpair_t;
 #endif
 
 #define TICKET_SHIFT    (sizeof(__ticket_t) * 8)
@@ -18,14 +20,14 @@ typedef u16 __ticket_t;
 
 typedef struct arch_spinlock {
         union {
-                unsigned int slock;
+                __ticketpair_t head_tail;
                 struct __raw_tickets {
                         __ticket_t head, tail;
                 } tickets;
         };
 } arch_spinlock_t;
 
-#define __ARCH_SPIN_LOCK_UNLOCKED       { { .slock = 0 } }
+#define __ARCH_SPIN_LOCK_UNLOCKED       { { 0 } }
 
 #include <asm/rwlock.h>