1/*
2 * ia64 implementation of the mutex fastpath.
3 *
4 * Copyright (C) 2006 Ken Chen <kenneth.w.chen@intel.com>
5 *
6 */
7
8#ifndef _ASM_MUTEX_H
9#define _ASM_MUTEX_H
10
11/**
12 *  __mutex_fastpath_lock - try to take the lock by moving the count
13 *                          from 1 to a 0 value
14 *  @count: pointer of type atomic_t
15 *  @fail_fn: function to call if the original value was not 1
16 *
17 * Change the count from 1 to a value lower than 1, and call <fail_fn> if
18 * it wasn't 1 originally. This function MUST leave the value lower than
19 * 1 even when the "1" assertion wasn't true.
20 */
21static inline void
22__mutex_fastpath_lock(atomic_t *count, void (*fail_fn)(atomic_t *))
23{
24	if (unlikely(ia64_fetchadd4_acq(count, -1) != 1))
25		fail_fn(count);
26}
27
28/**
29 *  __mutex_fastpath_lock_retval - try to take the lock by moving the count
30 *                                 from 1 to a 0 value
31 *  @count: pointer of type atomic_t
32 *  @fail_fn: function to call if the original value was not 1
33 *
34 * Change the count from 1 to a value lower than 1, and call <fail_fn> if
35 * it wasn't 1 originally. This function returns 0 if the fastpath succeeds,
36 * or anything the slow path function returns.
37 */
38static inline int
39__mutex_fastpath_lock_retval(atomic_t *count, int (*fail_fn)(atomic_t *))
40{
41	if (unlikely(ia64_fetchadd4_acq(count, -1) != 1))
42		return fail_fn(count);
43	return 0;
44}
45
46/**
47 *  __mutex_fastpath_unlock - try to promote the count from 0 to 1
48 *  @count: pointer of type atomic_t
49 *  @fail_fn: function to call if the original value was not 0
50 *
51 * Try to promote the count from 0 to 1. If it wasn't 0, call <fail_fn>.
52 * In the failure case, this function is allowed to either set the value to
53 * 1, or to set it to a value lower than 1.
54 *
55 * If the implementation sets it to a value of lower than 1, then the
56 * __mutex_slowpath_needs_to_unlock() macro needs to return 1, it needs
57 * to return 0 otherwise.
58 */
59static inline void
60__mutex_fastpath_unlock(atomic_t *count, void (*fail_fn)(atomic_t *))
61{
62	int ret = ia64_fetchadd4_rel(count, 1);
63	if (unlikely(ret < 0))
64		fail_fn(count);
65}
66
67#define __mutex_slowpath_needs_to_unlock()		1
68
69/**
70 * __mutex_fastpath_trylock - try to acquire the mutex, without waiting
71 *
72 *  @count: pointer of type atomic_t
73 *  @fail_fn: fallback function
74 *
75 * Change the count from 1 to a value lower than 1, and return 0 (failure)
76 * if it wasn't 1 originally, or return 1 (success) otherwise. This function
77 * MUST leave the value lower than 1 even when the "1" assertion wasn't true.
78 * Additionally, if the value was < 0 originally, this function must not leave
79 * it to 0 on failure.
80 *
81 * If the architecture has no effective trylock variant, it should call the
82 * <fail_fn> spinlock-based trylock variant unconditionally.
83 */
84static inline int
85__mutex_fastpath_trylock(atomic_t *count, int (*fail_fn)(atomic_t *))
86{
87	if (cmpxchg_acq(count, 1, 0) == 1)
88		return 1;
89	return 0;
90}
91
92#endif
93