101 lines
2.9 KiB
C
101 lines
2.9 KiB
C
/*
|
|
* Assembly implementation of the mutex fastpath, based on atomic
|
|
* decrement/increment.
|
|
*
|
|
* started by Ingo Molnar:
|
|
*
|
|
* Copyright (C) 2004, 2005, 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
|
|
*/
|
|
#ifndef _ASM_X86_MUTEX_64_H
|
|
#define _ASM_X86_MUTEX_64_H
|
|
|
|
/**
|
|
* __mutex_fastpath_lock - decrement and call function if negative
|
|
* @v: pointer of type atomic_t
|
|
* @fail_fn: function to call if the result is negative
|
|
*
|
|
* Atomically decrements @v and calls <fail_fn> if the result is negative.
|
|
*/
|
|
#define __mutex_fastpath_lock(v, fail_fn) \
|
|
do { \
|
|
unsigned long dummy; \
|
|
\
|
|
typecheck(atomic_t *, v); \
|
|
typecheck_fn(void (*)(atomic_t *), fail_fn); \
|
|
\
|
|
asm volatile(LOCK_PREFIX " decl (%%rdi)\n" \
|
|
" jns 1f \n" \
|
|
" call " #fail_fn "\n" \
|
|
"1:" \
|
|
: "=D" (dummy) \
|
|
: "D" (v) \
|
|
: "rax", "rsi", "rdx", "rcx", \
|
|
"r8", "r9", "r10", "r11", "memory"); \
|
|
} while (0)
|
|
|
|
/**
|
|
* __mutex_fastpath_lock_retval - try to take the lock by moving the count
|
|
* from 1 to a 0 value
|
|
* @count: pointer of type atomic_t
|
|
* @fail_fn: function to call if the original value was not 1
|
|
*
|
|
* Change the count from 1 to a value lower than 1, and call <fail_fn> if
|
|
* it wasn't 1 originally. This function returns 0 if the fastpath succeeds,
|
|
* or anything the slow path function returns
|
|
*/
|
|
static inline int __mutex_fastpath_lock_retval(atomic_t *count,
|
|
int (*fail_fn)(atomic_t *))
|
|
{
|
|
if (unlikely(atomic_dec_return(count) < 0))
|
|
return fail_fn(count);
|
|
else
|
|
return 0;
|
|
}
|
|
|
|
/**
|
|
* __mutex_fastpath_unlock - increment and call function if nonpositive
|
|
* @v: pointer of type atomic_t
|
|
* @fail_fn: function to call if the result is nonpositive
|
|
*
|
|
* Atomically increments @v and calls <fail_fn> if the result is nonpositive.
|
|
*/
|
|
#define __mutex_fastpath_unlock(v, fail_fn) \
|
|
do { \
|
|
unsigned long dummy; \
|
|
\
|
|
typecheck(atomic_t *, v); \
|
|
typecheck_fn(void (*)(atomic_t *), fail_fn); \
|
|
\
|
|
asm volatile(LOCK_PREFIX " incl (%%rdi)\n" \
|
|
" jg 1f\n" \
|
|
" call " #fail_fn "\n" \
|
|
"1:" \
|
|
: "=D" (dummy) \
|
|
: "D" (v) \
|
|
: "rax", "rsi", "rdx", "rcx", \
|
|
"r8", "r9", "r10", "r11", "memory"); \
|
|
} while (0)
|
|
|
|
#define __mutex_slowpath_needs_to_unlock() 1
|
|
|
|
/**
|
|
* __mutex_fastpath_trylock - try to acquire the mutex, without waiting
|
|
*
|
|
* @count: pointer of type atomic_t
|
|
* @fail_fn: fallback function
|
|
*
|
|
* Change the count from 1 to 0 and return 1 (success), or return 0 (failure)
|
|
* if it wasn't 1 originally. [the fallback function is never used on
|
|
* x86_64, because all x86_64 CPUs have a CMPXCHG instruction.]
|
|
*/
|
|
static inline int __mutex_fastpath_trylock(atomic_t *count,
|
|
int (*fail_fn)(atomic_t *))
|
|
{
|
|
if (likely(atomic_cmpxchg(count, 1, 0) == 1))
|
|
return 1;
|
|
else
|
|
return 0;
|
|
}
|
|
|
|
#endif /* _ASM_X86_MUTEX_64_H */
|