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Commit | Line | Data |
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76a50749 UD |
1 | Conditional Variable pseudocode. |
2 | ================================ | |
3 | ||
4 | int pthread_cond_timedwait (pthread_cond_t *cv, pthread_mutex_t *mutex); | |
5 | int pthread_cond_signal (pthread_cond_t *cv); | |
6 | int pthread_cond_broadcast (pthread_cond_t *cv); | |
7 | ||
8 | struct pthread_cond_t { | |
9 | ||
05df18c3 | 10 | unsigned int cond_lock; |
76a50749 UD |
11 | |
12 | internal mutex | |
13 | ||
05df18c3 | 14 | uint64_t total_seq; |
76a50749 | 15 | |
05df18c3 | 16 | Total number of threads using the conditional variable. |
76a50749 | 17 | |
05df18c3 | 18 | uint64_t wakeup_seq; |
76a50749 | 19 | |
05df18c3 UD |
20 | sequence number for next wakeup. |
21 | ||
22 | uint64_t woken_seq; | |
23 | ||
24 | sequence number of last woken thread. | |
76a50749 UD |
25 | |
26 | } | |
27 | ||
76a50749 | 28 | |
05df18c3 UD |
29 | |
30 | cleanup_handler(cv) | |
31 | { | |
32 | lll_lock(cv->lock); | |
33 | ||
34 | ++cv->wakeup_seq; | |
35 | ++cv->woken_seq; | |
36 | ||
37 | lll_unlock(cv->lock); | |
38 | } | |
39 | ||
40 | ||
41 | cond_timedwait(cv, mutex, timeout): | |
76a50749 UD |
42 | { |
43 | lll_lock(cv->lock); | |
44 | mutex_unlock(mutex); | |
45 | ||
05df18c3 UD |
46 | cleanup_push |
47 | ||
48 | ++cv->total_seq; | |
49 | val = seq = cv->wakeup_seq; | |
50 | ||
51 | while (1) { | |
52 | ||
53 | lll_unlock(cv->lock); | |
54 | ||
55 | enable_async | |
76a50749 | 56 | |
05df18c3 | 57 | ret = FUTEX_WAIT(cv->wakeup_seq, val, timeout); |
76a50749 | 58 | |
05df18c3 | 59 | restore_async |
76a50749 | 60 | |
05df18c3 | 61 | lll_lock(cv->lock); |
76a50749 | 62 | |
05df18c3 | 63 | val = cv->wakeup_seq; |
76a50749 | 64 | |
05df18c3 | 65 | if (cv->woken_seq >= seq && cv->woken_seq < val) { |
76a50749 | 66 | ret = 0; |
05df18c3 UD |
67 | break; |
68 | } | |
69 | ||
70 | if (ret == TIMEDOUT) { | |
71 | ++cv->wakeup_seq; | |
72 | break; | |
73 | } | |
76a50749 | 74 | } |
05df18c3 UD |
75 | |
76 | ++cv->woken_seq; | |
77 | ||
76a50749 | 78 | lll_unlock(cv->lock); |
05df18c3 UD |
79 | |
80 | cleanup_pop | |
81 | ||
76a50749 UD |
82 | mutex_lock(mutex); |
83 | ||
84 | return ret; | |
85 | } | |
86 | ||
87 | cond_signal(cv) | |
88 | { | |
76a50749 | 89 | lll_lock(cv->lock); |
05df18c3 UD |
90 | |
91 | if (cv->total_seq > cv->wakeup_seq) { | |
92 | ++cv->wakeup_seq; | |
93 | FUTEX_WAKE(cv->wakeup_seq, 1); | |
76a50749 | 94 | } |
05df18c3 | 95 | |
76a50749 | 96 | lll_unlock(cv->lock); |
76a50749 UD |
97 | } |
98 | ||
99 | cond_broadcast(cv) | |
100 | { | |
76a50749 | 101 | lll_lock(cv->lock); |
05df18c3 UD |
102 | |
103 | if (cv->total_seq > cv->wakeup_seq) { | |
104 | cv->wakeup_seq = cv->total_seq; | |
105 | FUTEX_WAKE(cv->wakeup_seq, ALL); | |
76a50749 | 106 | } |
05df18c3 | 107 | |
76a50749 | 108 | lll_unlock(cv->lock); |
76a50749 | 109 | } |