[mirror_ubuntu-artful-kernel.git] / arch / x86 / include / asm / mutex_64.h

/*
 * 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 */
Commit	Line	Data
b8aa0361 IM	1	/*
	2	* Assembly implementation of the mutex fastpath, based on atomic
	3	* decrement/increment.
	4	*
	5	* started by Ingo Molnar:
	6	*
	7	* Copyright (C) 2004, 2005, 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
	8	*/
1965aae3 PA	9	#ifndef _ASM_X86_MUTEX_64_H
1965aae3 PA	10	#define _ASM_X86_MUTEX_64_H
b8aa0361 IM	11
	12	/**
	13	* __mutex_fastpath_lock - decrement and call function if negative
	14	* @v: pointer of type atomic_t
	15	* @fail_fn: function to call if the result is negative
	16	*
	17	* Atomically decrements @v and calls <fail_fn> if the result is negative.
	18	*/
2c4e8830 JP	19	#define __mutex_fastpath_lock(v, fail_fn) \
	20	do { \
	21	unsigned long dummy; \
	22	\
	23	typecheck(atomic_t *, v); \
	24	typecheck_fn(void ()(atomic_t ), fail_fn); \
	25	\
	26	asm volatile(LOCK_PREFIX " decl (%%rdi)\n" \
	27	" jns 1f \n" \
	28	" call " #fail_fn "\n" \
	29	"1:" \
	30	: "=D" (dummy) \
	31	: "D" (v) \
	32	: "rax", "rsi", "rdx", "rcx", \
	33	"r8", "r9", "r10", "r11", "memory"); \
b8aa0361 IM	34	} while (0)
	35
	36	/**
	37	* __mutex_fastpath_lock_retval - try to take the lock by moving the count
	38	* from 1 to a 0 value
	39	* @count: pointer of type atomic_t
	40	* @fail_fn: function to call if the original value was not 1
	41	*
	42	* Change the count from 1 to a value lower than 1, and call <fail_fn> if
	43	* it wasn't 1 originally. This function returns 0 if the fastpath succeeds,
	44	* or anything the slow path function returns
	45	*/
2c4e8830 JP	46	static inline int __mutex_fastpath_lock_retval(atomic_t *count,
2c4e8830 JP	47	int (fail_fn)(atomic_t ))
b8aa0361 IM	48	{
	49	if (unlikely(atomic_dec_return(count) < 0))
	50	return fail_fn(count);
	51	else
	52	return 0;
	53	}
	54
	55	/**
	56	* __mutex_fastpath_unlock - increment and call function if nonpositive
	57	* @v: pointer of type atomic_t
	58	* @fail_fn: function to call if the result is nonpositive
	59	*
	60	* Atomically increments @v and calls <fail_fn> if the result is nonpositive.
	61	*/
2c4e8830 JP	62	#define __mutex_fastpath_unlock(v, fail_fn) \
	63	do { \
	64	unsigned long dummy; \
	65	\
	66	typecheck(atomic_t *, v); \
	67	typecheck_fn(void ()(atomic_t ), fail_fn); \
	68	\
	69	asm volatile(LOCK_PREFIX " incl (%%rdi)\n" \
	70	" jg 1f\n" \
	71	" call " #fail_fn "\n" \
	72	"1:" \
	73	: "=D" (dummy) \
	74	: "D" (v) \
	75	: "rax", "rsi", "rdx", "rcx", \
	76	"r8", "r9", "r10", "r11", "memory"); \
b8aa0361 IM	77	} while (0)
	78
	79	#define __mutex_slowpath_needs_to_unlock() 1
	80
	81	/**
	82	* __mutex_fastpath_trylock - try to acquire the mutex, without waiting
	83	*
	84	* @count: pointer of type atomic_t
	85	* @fail_fn: fallback function
	86	*
	87	* Change the count from 1 to 0 and return 1 (success), or return 0 (failure)
	88	* if it wasn't 1 originally. [the fallback function is never used on
	89	* x86_64, because all x86_64 CPUs have a CMPXCHG instruction.]
	90	*/
2c4e8830 JP	91	static inline int __mutex_fastpath_trylock(atomic_t *count,
2c4e8830 JP	92	int (fail_fn)(atomic_t ))
b8aa0361	93	{
4cec8736	94	if (likely(atomic_cmpxchg(count, 1, 0) == 1))
b8aa0361 IM	95	return 1;
	96	else
	97	return 0;
	98	}
	99
1965aae3	100	#endif /* _ASM_X86_MUTEX_64_H */