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Commit 74e91604 authored by Jan Beulich's avatar Jan Beulich Committed by Ingo Molnar
Browse files

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: default avatarJan Beulich <jbeulich@novell.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 08f5fcbe

include/asm-x86/spinlock.h

+7 −7
Original line number Diff line number Diff line
@@ -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"