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x86/cmpxchg: add a locked add() helper 

Mostly to remove some conditional code in spinlock.h.

Signed-off-by: Jeremy Fitzhardinge <jeremy@goop.org>
This commit is contained in:
Jeremy Fitzhardinge 2011-09-28 11:49:28 -07:00
parent 4a7f340c6a
commit 3d94ae0c70
2 changed files with 43 additions and 14 deletions
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42
arch/x86/include/asm/cmpxchg.h
View File

@ -14,6 +14,8 @@ extern void __cmpxchg_wrong_size(void)
__compiletime_error("Bad argument size for cmpxchg");
extern void __xadd_wrong_size(void)
__compiletime_error("Bad argument size for xadd");
extern void __add_wrong_size(void)
__compiletime_error("Bad argument size for add");
/*
* Constants for operation sizes. On 32-bit, the 64-bit size it set to
@ -207,4 +209,44 @@ extern void __xadd_wrong_size(void)
#define xadd_sync(ptr, inc) __xadd((ptr), (inc), "lock; ")
#define xadd_local(ptr, inc) __xadd((ptr), (inc), "")
#define __add(ptr, inc, lock) \
({ \
__typeof__ (*(ptr)) __ret = (inc); \
switch (sizeof(*(ptr))) { \
case __X86_CASE_B: \
asm volatile (lock "addb %b1, %0\n" \
: "+m" (*(ptr)) : "ri" (inc) \
: "memory", "cc"); \
break; \
case __X86_CASE_W: \
asm volatile (lock "addw %w1, %0\n" \
: "+m" (*(ptr)) : "ri" (inc) \
: "memory", "cc"); \
break; \
case __X86_CASE_L: \
asm volatile (lock "addl %1, %0\n" \
: "+m" (*(ptr)) : "ri" (inc) \
: "memory", "cc"); \
break; \
case __X86_CASE_Q: \
asm volatile (lock "addq %1, %0\n" \
: "+m" (*(ptr)) : "ri" (inc) \
: "memory", "cc"); \
break; \
default: \
__add_wrong_size(); \
} \
__ret; \
})
/*
* add_*() adds "inc" to "*ptr"
*
* __add() takes a lock prefix
* add_smp() is locked when multiple CPUs are online
* add_sync() is always locked
*/
#define add_smp(ptr, inc) __add((ptr), (inc), LOCK_PREFIX)
#define add_sync(ptr, inc) __add((ptr), (inc), "lock; ")
#endif /* ASM_X86_CMPXCHG_H */

15
arch/x86/include/asm/spinlock.h
View File

@ -79,23 +79,10 @@ static __always_inline int __ticket_spin_trylock(arch_spinlock_t *lock)
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->head_tail)
:
: "memory", "cc");
__add(&lock->tickets.head, 1, UNLOCK_LOCK_PREFIX);
}
#else
static __always_inline void __ticket_spin_unlock(arch_spinlock_t *lock)
{
asm volatile(UNLOCK_LOCK_PREFIX "incw %0"
: "+m" (lock->head_tail)
:
: "memory", "cc");
}
#endif
static inline int __ticket_spin_is_locked(arch_spinlock_t *lock)
{