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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 */
9#ifndef _ASM_X86_MUTEX_64_H
10#define _ASM_X86_MUTEX_64_H
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 */
19#ifdef CC_HAVE_ASM_GOTO
20static inline void __mutex_fastpath_lock(atomic_t *v,
21 void (*fail_fn)(atomic_t *))
22{
23 asm_volatile_goto(LOCK_PREFIX " decl %0\n"
24 " jns %l[exit]\n"
25 : : "m" (v->counter)
26 : "memory", "cc"
27 : exit);
28 fail_fn(v);
29exit:
30 return;
31}
32#else
33#define __mutex_fastpath_lock(v, fail_fn) \
34do { \
35 unsigned long dummy; \
36 \
37 typecheck(atomic_t *, v); \
38 typecheck_fn(void (*)(atomic_t *), fail_fn); \
39 \
40 asm volatile(LOCK_PREFIX " decl (%%rdi)\n" \
41 " jns 1f \n" \
42 " call " #fail_fn "\n" \
43 "1:" \
44 : "=D" (dummy) \
45 : "D" (v) \
46 : "rax", "rsi", "rdx", "rcx", \
47 "r8", "r9", "r10", "r11", "memory"); \
48} while (0)
49#endif
50
51/**
52 * __mutex_fastpath_lock_retval - try to take the lock by moving the count
53 * from 1 to a 0 value
54 * @count: pointer of type atomic_t
55 *
56 * Change the count from 1 to a value lower than 1. This function returns 0
57 * if the fastpath succeeds, or -1 otherwise.
58 */
59static inline int __mutex_fastpath_lock_retval(atomic_t *count)
60{
61 if (unlikely(atomic_dec_return(count) < 0))
62 return -1;
63 else
64 return 0;
65}
66
67/**
68 * __mutex_fastpath_unlock - increment and call function if nonpositive
69 * @v: pointer of type atomic_t
70 * @fail_fn: function to call if the result is nonpositive
71 *
72 * Atomically increments @v and calls <fail_fn> if the result is nonpositive.
73 */
74#ifdef CC_HAVE_ASM_GOTO
75static inline void __mutex_fastpath_unlock(atomic_t *v,
76 void (*fail_fn)(atomic_t *))
77{
78 asm_volatile_goto(LOCK_PREFIX " incl %0\n"
79 " jg %l[exit]\n"
80 : : "m" (v->counter)
81 : "memory", "cc"
82 : exit);
83 fail_fn(v);
84exit:
85 return;
86}
87#else
88#define __mutex_fastpath_unlock(v, fail_fn) \
89do { \
90 unsigned long dummy; \
91 \
92 typecheck(atomic_t *, v); \
93 typecheck_fn(void (*)(atomic_t *), fail_fn); \
94 \
95 asm volatile(LOCK_PREFIX " incl (%%rdi)\n" \
96 " jg 1f\n" \
97 " call " #fail_fn "\n" \
98 "1:" \
99 : "=D" (dummy) \
100 : "D" (v) \
101 : "rax", "rsi", "rdx", "rcx", \
102 "r8", "r9", "r10", "r11", "memory"); \
103} while (0)
104#endif
105
106#define __mutex_slowpath_needs_to_unlock() 1
107
108/**
109 * __mutex_fastpath_trylock - try to acquire the mutex, without waiting
110 *
111 * @count: pointer of type atomic_t
112 * @fail_fn: fallback function
113 *
114 * Change the count from 1 to 0 and return 1 (success), or return 0 (failure)
115 * if it wasn't 1 originally. [the fallback function is never used on
116 * x86_64, because all x86_64 CPUs have a CMPXCHG instruction.]
117 */
118static inline int __mutex_fastpath_trylock(atomic_t *count,
119 int (*fail_fn)(atomic_t *))
120{
121 if (likely(atomic_cmpxchg(count, 1, 0) == 1))
122 return 1;
123 else
124 return 0;
125}
126
127#endif /* _ASM_X86_MUTEX_64_H */
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 */
9#ifndef _ASM_X86_MUTEX_64_H
10#define _ASM_X86_MUTEX_64_H
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 */
19#define __mutex_fastpath_lock(v, fail_fn) \
20do { \
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"); \
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 */
46static inline int __mutex_fastpath_lock_retval(atomic_t *count,
47 int (*fail_fn)(atomic_t *))
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 */
62#define __mutex_fastpath_unlock(v, fail_fn) \
63do { \
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"); \
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 */
91static inline int __mutex_fastpath_trylock(atomic_t *count,
92 int (*fail_fn)(atomic_t *))
93{
94 if (likely(atomic_cmpxchg(count, 1, 0) == 1))
95 return 1;
96 else
97 return 0;
98}
99
100#endif /* _ASM_X86_MUTEX_64_H */