1/* Acquire a rwlock for writing. Generic version.
2 Copyright (C) 2002-2024 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. */
28int
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. No one 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
102int
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}
108weak_alias (__pthread_rwlock_timedwrlock, pthread_rwlock_timedwrlock)
109
110int
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}
117weak_alias (__pthread_rwlock_clockwrlock, pthread_rwlock_clockwrlock)
118

source code of glibc/sysdeps/htl/pt-rwlock-timedwrlock.c