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>
diff --git a/arch/x86/include/asm/spinlock.h b/arch/x86/include/asm/spinlock.h
index b69e0b4..f5695ee 100644
--- a/arch/x86/include/asm/spinlock.h
+++ b/arch/x86/include/asm/spinlock.h
@@ -69,60 +69,33 @@
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;
+ arch_spinlock_t old, 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");
+ 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");
}