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 */
21 static inline void
__mutex_fastpath_lock(atomic_t * count,void (* fail_fn)(atomic_t *))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 *
33 * Change the count from 1 to a value lower than 1. This function returns 0
34 * if the fastpath succeeds, or -1 otherwise.
35 */
36 static inline int
__mutex_fastpath_lock_retval(atomic_t * count)37 __mutex_fastpath_lock_retval(atomic_t *count)
38 {
39 if (unlikely(ia64_fetchadd4_acq(count, -1) != 1))
40 return -1;
41 return 0;
42 }
43
44 /**
45 * __mutex_fastpath_unlock - try to promote the count from 0 to 1
46 * @count: pointer of type atomic_t
47 * @fail_fn: function to call if the original value was not 0
48 *
49 * Try to promote the count from 0 to 1. If it wasn't 0, call <fail_fn>.
50 * In the failure case, this function is allowed to either set the value to
51 * 1, or to set it to a value lower than 1.
52 *
53 * If the implementation sets it to a value of lower than 1, then the
54 * __mutex_slowpath_needs_to_unlock() macro needs to return 1, it needs
55 * to return 0 otherwise.
56 */
57 static inline void
__mutex_fastpath_unlock(atomic_t * count,void (* fail_fn)(atomic_t *))58 __mutex_fastpath_unlock(atomic_t *count, void (*fail_fn)(atomic_t *))
59 {
60 int ret = ia64_fetchadd4_rel(count, 1);
61 if (unlikely(ret < 0))
62 fail_fn(count);
63 }
64
65 #define __mutex_slowpath_needs_to_unlock() 1
66
67 /**
68 * __mutex_fastpath_trylock - try to acquire the mutex, without waiting
69 *
70 * @count: pointer of type atomic_t
71 * @fail_fn: fallback function
72 *
73 * Change the count from 1 to a value lower than 1, and return 0 (failure)
74 * if it wasn't 1 originally, or return 1 (success) otherwise. This function
75 * MUST leave the value lower than 1 even when the "1" assertion wasn't true.
76 * Additionally, if the value was < 0 originally, this function must not leave
77 * it to 0 on failure.
78 *
79 * If the architecture has no effective trylock variant, it should call the
80 * <fail_fn> spinlock-based trylock variant unconditionally.
81 */
82 static inline int
__mutex_fastpath_trylock(atomic_t * count,int (* fail_fn)(atomic_t *))83 __mutex_fastpath_trylock(atomic_t *count, int (*fail_fn)(atomic_t *))
84 {
85 if (cmpxchg_acq(count, 1, 0) == 1)
86 return 1;
87 return 0;
88 }
89
90 #endif
91