x86: ticket spin locks: reduce instruction dependencies
Reduce the amount of partial register accesses in the NR_CPUS < 256
case, and slightly weaken resource dependencies in the other case.
Signed-off-by: Jan Beulich <jbeulich@novell.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/include/asm-x86/spinlock.h b/include/asm-x86/spinlock.h
index 63d3b61..b5a4551 100644
--- a/include/asm-x86/spinlock.h
+++ b/include/asm-x86/spinlock.h
@@ -21,8 +21,10 @@
#ifdef CONFIG_X86_32
# define LOCK_PTR_REG "a"
+# define REG_PTR_MODE "k"
#else
# define LOCK_PTR_REG "D"
+# define REG_PTR_MODE "q"
#endif
#if defined(CONFIG_X86_32) && \
@@ -77,19 +79,17 @@
static __always_inline int __ticket_spin_trylock(raw_spinlock_t *lock)
{
- int tmp;
- short new;
+ int tmp, new;
- asm volatile("movw %2,%w0\n\t"
+ 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"
- "movw %w0,%w1\n\t"
- "incb %h1\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)
+ : "=&a" (tmp), "=&q" (new), "+m" (lock->slock)
:
: "memory", "cc");
@@ -136,8 +136,8 @@
"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"
- "addl $0x00010000, %1\n\t"
LOCK_PREFIX "cmpxchgl %1,%2\n\t"
"1:"
"sete %b1\n\t"