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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 |
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, |
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, |
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 */ |