blob: 4845251c7586c9667cd33c38af3701910d65eaa8 (
plain) (
blame)
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
131
132
133
134
|
Conditional Variable pseudocode.
================================
int pthread_cond_timedwait (pthread_cond_t *cv, pthread_mutex_t *mutex);
int pthread_cond_signal (pthread_cond_t *cv);
int pthread_cond_broadcast (pthread_cond_t *cv);
struct pthread_cond_t {
unsigned int cond_lock;
internal mutex
uint64_t total_seq;
Total number of threads using the conditional variable.
uint64_t wakeup_seq;
sequence number for next wakeup.
uint64_t woken_seq;
sequence number of last woken thread.
uint32_t broadcast_seq;
}
struct cv_data {
pthread_cond_t *cv;
uint32_t bc_seq
}
cleanup_handler(cv_data)
{
cv = cv_data->cv;
lll_lock(cv->lock);
if (cv_data->bc_seq == cv->broadcast_seq) {
++cv->wakeup_seq;
++cv->woken_seq;
}
/* make sure no signal gets lost. */
FUTEX_WAKE(cv->wakeup_seq, ALL);
lll_unlock(cv->lock);
}
cond_timedwait(cv, mutex, timeout):
{
lll_lock(cv->lock);
mutex_unlock(mutex);
cleanup_push
++cv->total_seq;
val = seq = cv->wakeup_seq;
cv_data.bc = cv->broadcast_seq;
cv_data.cv = cv;
while (1) {
lll_unlock(cv->lock);
enable_async(&cv_data);
ret = FUTEX_WAIT(cv->wakeup_seq, val, timeout);
restore_async
lll_lock(cv->lock);
if (bc != cv->broadcast_seq)
goto bc_out;
val = cv->wakeup_seq;
if (val != seq && cv->woken_seq != val) {
ret = 0;
break;
}
if (ret == TIMEDOUT) {
++cv->wakeup_seq;
break;
}
}
++cv->woken_seq;
bc_out:
lll_unlock(cv->lock);
cleanup_pop
mutex_lock(mutex);
return ret;
}
cond_signal(cv)
{
lll_lock(cv->lock);
if (cv->total_seq > cv->wakeup_seq) {
++cv->wakeup_seq;
FUTEX_WAKE(cv->wakeup_seq, 1);
}
lll_unlock(cv->lock);
}
cond_broadcast(cv)
{
lll_lock(cv->lock);
if (cv->total_seq > cv->wakeup_seq) {
cv->wakeup_seq = cv->total_seq;
cv->woken_seq = cv->total_seq;
++cv->broadcast_seq;
FUTEX_WAKE(cv->wakeup_seq, ALL);
}
lll_unlock(cv->lock);
}
|
