1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
|
/*
* Assembly implementation of the mutex fastpath, based on atomic
* decrement/increment.
*
* started by Ingo Molnar:
*
* Copyright (C) 2004, 2005, 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
*/
#ifndef _ASM_X86_MUTEX_64_H
#define _ASM_X86_MUTEX_64_H
/**
* __mutex_fastpath_lock - decrement and call function if negative
* @v: pointer of type atomic_t
* @fail_fn: function to call if the result is negative
*
* Atomically decrements @v and calls <fail_fn> if the result is negative.
*/
#ifdef CC_HAVE_ASM_GOTO
static inline void __mutex_fastpath_lock(atomic_t *v,
void (*fail_fn)(atomic_t *))
{
asm volatile goto(LOCK_PREFIX " decl %0\n"
" jns %l[exit]\n"
: : "m" (v->counter)
: "memory", "cc"
: exit);
fail_fn(v);
exit:
return;
}
#else
#define __mutex_fastpath_lock(v, fail_fn) \
do { \
unsigned long dummy; \
\
typecheck(atomic_t *, v); \
typecheck_fn(void (*)(atomic_t *), fail_fn); \
\
asm volatile(LOCK_PREFIX " decl (%%rdi)\n" \
" jns 1f \n" \
" call " #fail_fn "\n" \
"1:" \
: "=D" (dummy) \
: "D" (v) \
: "rax", "rsi", "rdx", "rcx", \
"r8", "r9", "r10", "r11", "memory"); \
} while (0)
#endif
/**
* __mutex_fastpath_lock_retval - try to take the lock by moving the count
* from 1 to a 0 value
* @count: pointer of type atomic_t
* @fail_fn: function to call if the original value was not 1
*
* Change the count from 1 to a value lower than 1, and call <fail_fn> if
* it wasn't 1 originally. This function returns 0 if the fastpath succeeds,
* or anything the slow path function returns
*/
static inline int __mutex_fastpath_lock_retval(atomic_t *count,
int (*fail_fn)(atomic_t *))
{
if (unlikely(atomic_dec_return(count) < 0))
return fail_fn(count);
else
return 0;
}
/**
* __mutex_fastpath_unlock - increment and call function if nonpositive
* @v: pointer of type atomic_t
* @fail_fn: function to call if the result is nonpositive
*
* Atomically increments @v and calls <fail_fn> if the result is nonpositive.
*/
#ifdef CC_HAVE_ASM_GOTO
static inline void __mutex_fastpath_unlock(atomic_t *v,
void (*fail_fn)(atomic_t *))
{
asm volatile goto(LOCK_PREFIX " incl %0\n"
" jg %l[exit]\n"
: : "m" (v->counter)
: "memory", "cc"
: exit);
fail_fn(v);
exit:
return;
}
#else
#define __mutex_fastpath_unlock(v, fail_fn) \
do { \
unsigned long dummy; \
\
typecheck(atomic_t *, v); \
typecheck_fn(void (*)(atomic_t *), fail_fn); \
\
asm volatile(LOCK_PREFIX " incl (%%rdi)\n" \
" jg 1f\n" \
" call " #fail_fn "\n" \
"1:" \
: "=D" (dummy) \
: "D" (v) \
: "rax", "rsi", "rdx", "rcx", \
"r8", "r9", "r10", "r11", "memory"); \
} while (0)
#endif
#define __mutex_slowpath_needs_to_unlock() 1
/**
* __mutex_fastpath_trylock - try to acquire the mutex, without waiting
*
* @count: pointer of type atomic_t
* @fail_fn: fallback function
*
* Change the count from 1 to 0 and return 1 (success), or return 0 (failure)
* if it wasn't 1 originally. [the fallback function is never used on
* x86_64, because all x86_64 CPUs have a CMPXCHG instruction.]
*/
static inline int __mutex_fastpath_trylock(atomic_t *count,
int (*fail_fn)(atomic_t *))
{
if (likely(atomic_cmpxchg(count, 1, 0) == 1))
return 1;
else
return 0;
}
#endif /* _ASM_X86_MUTEX_64_H */
|
