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x86: ticket spin locks: reduce instruction dependencies

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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>
This commit is contained in:
Jan Beulich 2008-09-05 13:27:45 +01:00 • committed by Ingo Molnar
parent 08f5fcbe6e
commit 74e91604b2
1 changed files with 7 additions and 7 deletions

14
include/asm-x86/spinlock.h
View file

@ -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 void __ticket_spin_lock(raw_spinlock_t *lock)
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 @@ static __always_inline int __ticket_spin_trylock(raw_spinlock_t *lock)
"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"