1 | /* Acquire a rwlock for writing. Generic version. |
2 | Copyright (C) 2002-2022 Free Software Foundation, Inc. |
3 | This file is part of the GNU C Library. |
4 | |
5 | The GNU C Library is free software; you can redistribute it and/or |
6 | modify it under the terms of the GNU Lesser General Public |
7 | License as published by the Free Software Foundation; either |
8 | version 2.1 of the License, or (at your option) any later version. |
9 | |
10 | The GNU C Library is distributed in the hope that it will be useful, |
11 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
13 | Lesser General Public License for more details. |
14 | |
15 | You should have received a copy of the GNU Lesser General Public |
16 | License along with the GNU C Library; if not, see |
17 | <https://www.gnu.org/licenses/>. */ |
18 | |
19 | #include <pthread.h> |
20 | #include <assert.h> |
21 | #include <time.h> |
22 | |
23 | #include <pt-internal.h> |
24 | |
25 | /* Acquire RWLOCK for writing blocking until *ABSTIME if we cannot get |
26 | it. As a special GNU extension, if ABSTIME is NULL then the wait |
27 | shall not time out. */ |
28 | int |
29 | __pthread_rwlock_timedwrlock_internal (struct __pthread_rwlock *rwlock, |
30 | clockid_t clockid, |
31 | const struct timespec *abstime) |
32 | { |
33 | error_t err; |
34 | int drain; |
35 | struct __pthread *self; |
36 | |
37 | __pthread_spin_wait (&rwlock->__lock); |
38 | if (__pthread_spin_trylock (&rwlock->__held) == 0) |
39 | /* Successfully acquired the lock. */ |
40 | { |
41 | assert (rwlock->__readerqueue == 0); |
42 | assert (rwlock->__writerqueue == 0); |
43 | assert (rwlock->__readers == 0); |
44 | |
45 | __pthread_spin_unlock (&rwlock->__lock); |
46 | return 0; |
47 | } |
48 | |
49 | /* The lock is busy. */ |
50 | |
51 | if (abstime != NULL && ! valid_nanoseconds (ns: abstime->tv_nsec)) |
52 | { |
53 | __pthread_spin_unlock (&rwlock->__lock); |
54 | return EINVAL; |
55 | } |
56 | |
57 | self = _pthread_self (); |
58 | |
59 | /* Add ourselves to the queue. */ |
60 | __pthread_enqueue (&rwlock->__writerqueue, self); |
61 | __pthread_spin_unlock (&rwlock->__lock); |
62 | |
63 | /* Block the thread. */ |
64 | if (abstime != NULL) |
65 | err = __pthread_timedblock (self, abstime, clockid); |
66 | else |
67 | { |
68 | err = 0; |
69 | __pthread_block (self); |
70 | } |
71 | |
72 | __pthread_spin_wait (&rwlock->__lock); |
73 | if (self->prevp == NULL) |
74 | /* Another thread removed us from the queue, which means a wakeup message |
75 | has been sent. It was either consumed while we were blocking, or |
76 | queued after we timed out and before we acquired the rwlock lock, in |
77 | which case the message queue must be drained. */ |
78 | drain = err ? 1 : 0; |
79 | else |
80 | { |
81 | /* We're still in the queue. Noone attempted to wake us up, i.e. we |
82 | timed out. */ |
83 | __pthread_dequeue (self); |
84 | drain = 0; |
85 | } |
86 | __pthread_spin_unlock (&rwlock->__lock); |
87 | |
88 | if (drain) |
89 | __pthread_block (self); |
90 | |
91 | if (err) |
92 | { |
93 | assert (err == ETIMEDOUT); |
94 | return err; |
95 | } |
96 | |
97 | assert (rwlock->__readers == 0); |
98 | |
99 | return 0; |
100 | } |
101 | |
102 | int |
103 | __pthread_rwlock_timedwrlock (struct __pthread_rwlock *rwlock, |
104 | const struct timespec *abstime) |
105 | { |
106 | return __pthread_rwlock_timedwrlock_internal (rwlock, CLOCK_REALTIME, abstime); |
107 | } |
108 | weak_alias (__pthread_rwlock_timedwrlock, pthread_rwlock_timedwrlock) |
109 | |
110 | int |
111 | __pthread_rwlock_clockwrlock (struct __pthread_rwlock *rwlock, |
112 | clockid_t clockid, |
113 | const struct timespec *abstime) |
114 | { |
115 | return __pthread_rwlock_timedwrlock_internal (rwlock, clockid, abstime); |
116 | } |
117 | weak_alias (__pthread_rwlock_clockwrlock, pthread_rwlock_clockwrlock) |
118 | |