Commit | Line | Data |
---|---|---|
620a6fd1 | 1 | /* |
f30c2269 | 2 | * include/asm-generic/mutex-dec.h |
620a6fd1 IM |
3 | * |
4 | * Generic implementation of the mutex fastpath, based on atomic | |
5 | * decrement/increment. | |
6 | */ | |
7 | #ifndef _ASM_GENERIC_MUTEX_DEC_H | |
8 | #define _ASM_GENERIC_MUTEX_DEC_H | |
9 | ||
10 | /** | |
11 | * __mutex_fastpath_lock - try to take the lock by moving the count | |
12 | * from 1 to a 0 value | |
13 | * @count: pointer of type atomic_t | |
14 | * @fail_fn: function to call if the original value was not 1 | |
15 | * | |
16 | * Change the count from 1 to a value lower than 1, and call <fail_fn> if | |
17 | * it wasn't 1 originally. This function MUST leave the value lower than | |
18 | * 1 even when the "1" assertion wasn't true. | |
19 | */ | |
e358c1a2 | 20 | static inline void |
144b2a91 | 21 | __mutex_fastpath_lock(atomic_t *count, void (*fail_fn)(atomic_t *)) |
e358c1a2 NP |
22 | { |
23 | if (unlikely(atomic_dec_return(count) < 0)) | |
24 | fail_fn(count); | |
e358c1a2 | 25 | } |
620a6fd1 IM |
26 | |
27 | /** | |
28 | * __mutex_fastpath_lock_retval - try to take the lock by moving the count | |
29 | * from 1 to a 0 value | |
30 | * @count: pointer of type atomic_t | |
620a6fd1 | 31 | * |
a41b56ef ML |
32 | * Change the count from 1 to a value lower than 1. This function returns 0 |
33 | * if the fastpath succeeds, or -1 otherwise. | |
620a6fd1 IM |
34 | */ |
35 | static inline int | |
a41b56ef | 36 | __mutex_fastpath_lock_retval(atomic_t *count) |
620a6fd1 IM |
37 | { |
38 | if (unlikely(atomic_dec_return(count) < 0)) | |
a41b56ef | 39 | return -1; |
a8ddac7e | 40 | return 0; |
620a6fd1 IM |
41 | } |
42 | ||
43 | /** | |
44 | * __mutex_fastpath_unlock - try to promote the count from 0 to 1 | |
45 | * @count: pointer of type atomic_t | |
46 | * @fail_fn: function to call if the original value was not 0 | |
47 | * | |
48 | * Try to promote the count from 0 to 1. If it wasn't 0, call <fail_fn>. | |
49 | * In the failure case, this function is allowed to either set the value to | |
50 | * 1, or to set it to a value lower than 1. | |
51 | * | |
52 | * If the implementation sets it to a value of lower than 1, then the | |
53 | * __mutex_slowpath_needs_to_unlock() macro needs to return 1, it needs | |
54 | * to return 0 otherwise. | |
55 | */ | |
e358c1a2 | 56 | static inline void |
144b2a91 | 57 | __mutex_fastpath_unlock(atomic_t *count, void (*fail_fn)(atomic_t *)) |
e358c1a2 | 58 | { |
e358c1a2 NP |
59 | if (unlikely(atomic_inc_return(count) <= 0)) |
60 | fail_fn(count); | |
61 | } | |
620a6fd1 IM |
62 | |
63 | #define __mutex_slowpath_needs_to_unlock() 1 | |
64 | ||
65 | /** | |
66 | * __mutex_fastpath_trylock - try to acquire the mutex, without waiting | |
67 | * | |
68 | * @count: pointer of type atomic_t | |
69 | * @fail_fn: fallback function | |
70 | * | |
71 | * Change the count from 1 to a value lower than 1, and return 0 (failure) | |
72 | * if it wasn't 1 originally, or return 1 (success) otherwise. This function | |
73 | * MUST leave the value lower than 1 even when the "1" assertion wasn't true. | |
74 | * Additionally, if the value was < 0 originally, this function must not leave | |
75 | * it to 0 on failure. | |
76 | * | |
77 | * If the architecture has no effective trylock variant, it should call the | |
78 | * <fail_fn> spinlock-based trylock variant unconditionally. | |
79 | */ | |
80 | static inline int | |
81 | __mutex_fastpath_trylock(atomic_t *count, int (*fail_fn)(atomic_t *)) | |
82 | { | |
a8ddac7e | 83 | if (likely(atomic_cmpxchg(count, 1, 0) == 1)) |
620a6fd1 | 84 | return 1; |
620a6fd1 | 85 | return 0; |
620a6fd1 IM |
86 | } |
87 | ||
88 | #endif |