1 | /* Wait on a semaphore with a timeout. Generic version. |
2 | Copyright (C) 2005-2022 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 <semaphore.h> |
20 | #include <errno.h> |
21 | #include <assert.h> |
22 | #include <time.h> |
23 | #include <hurdlock.h> |
24 | #include <hurd/hurd.h> |
25 | #include <sysdep-cancel.h> |
26 | |
27 | #include <pt-internal.h> |
28 | |
29 | #if !__HAVE_64B_ATOMICS |
30 | static void |
31 | __sem_wait_32_finish (struct new_sem *isem); |
32 | #endif |
33 | |
34 | static void |
35 | __sem_wait_cleanup (void *arg) |
36 | { |
37 | struct new_sem *isem = arg; |
38 | |
39 | #if __HAVE_64B_ATOMICS |
40 | atomic_fetch_add_relaxed (&isem->data, -((uint64_t) 1 << SEM_NWAITERS_SHIFT)); |
41 | #else |
42 | __sem_wait_32_finish (isem); |
43 | #endif |
44 | } |
45 | |
46 | int |
47 | __sem_timedwait_internal (sem_t *restrict sem, |
48 | clockid_t clock_id, |
49 | const struct timespec *restrict timeout) |
50 | { |
51 | struct new_sem *isem = (struct new_sem *) sem; |
52 | int err, ret = 0; |
53 | int flags = isem->pshared ? GSYNC_SHARED : 0; |
54 | |
55 | __pthread_testcancel (); |
56 | |
57 | if (__sem_waitfast (isem, 0) == 0) |
58 | return 0; |
59 | |
60 | int cancel_oldtype = LIBC_CANCEL_ASYNC(); |
61 | |
62 | #if __HAVE_64B_ATOMICS |
63 | uint64_t d = atomic_fetch_add_relaxed (&sem->data, |
64 | (uint64_t) 1 << SEM_NWAITERS_SHIFT); |
65 | |
66 | pthread_cleanup_push (__sem_wait_cleanup, isem); |
67 | |
68 | for (;;) |
69 | { |
70 | if ((d & SEM_VALUE_MASK) == 0) |
71 | { |
72 | /* No token, sleep. */ |
73 | if (timeout) |
74 | err = __lll_abstimed_wait_intr ( |
75 | ((unsigned int *) &sem->data) + SEM_VALUE_OFFSET, |
76 | 0, timeout, flags, clock_id); |
77 | else |
78 | err = __lll_wait_intr ( |
79 | ((unsigned int *) &sem->data) + SEM_VALUE_OFFSET, |
80 | 0, flags); |
81 | |
82 | if (err != 0) |
83 | { |
84 | /* Error, interruption or timeout, abort. */ |
85 | if (err == KERN_TIMEDOUT) |
86 | err = ETIMEDOUT; |
87 | if (err == KERN_INTERRUPTED) |
88 | err = EINTR; |
89 | ret = __hurd_fail (err); |
90 | __sem_wait_cleanup (arg: isem); |
91 | break; |
92 | } |
93 | |
94 | /* Token changed */ |
95 | d = atomic_load_relaxed (&sem->data); |
96 | } |
97 | else |
98 | { |
99 | /* Try to acquire and dequeue. */ |
100 | if (atomic_compare_exchange_weak_acquire (&sem->data, |
101 | &d, d - 1 - ((uint64_t) 1 << SEM_NWAITERS_SHIFT))) |
102 | { |
103 | /* Success */ |
104 | ret = 0; |
105 | break; |
106 | } |
107 | } |
108 | } |
109 | |
110 | pthread_cleanup_pop (0); |
111 | #else |
112 | unsigned int v; |
113 | |
114 | atomic_fetch_add_acquire (&isem->nwaiters, 1); |
115 | |
116 | pthread_cleanup_push (__sem_wait_cleanup, isem); |
117 | |
118 | v = atomic_load_relaxed (&isem->value); |
119 | do |
120 | { |
121 | do |
122 | { |
123 | do |
124 | { |
125 | if ((v & SEM_NWAITERS_MASK) != 0) |
126 | break; |
127 | } |
128 | while (!atomic_compare_exchange_weak_release (&isem->value, |
129 | &v, v | SEM_NWAITERS_MASK)); |
130 | |
131 | if ((v >> SEM_VALUE_SHIFT) == 0) |
132 | { |
133 | /* No token, sleep. */ |
134 | if (timeout) |
135 | err = __lll_abstimed_wait_intr (&isem->value, |
136 | SEM_NWAITERS_MASK, timeout, flags, clock_id); |
137 | else |
138 | err = __lll_wait_intr (&isem->value, |
139 | SEM_NWAITERS_MASK, flags); |
140 | |
141 | if (err != 0) |
142 | { |
143 | /* Error, interruption or timeout, abort. */ |
144 | if (err == KERN_TIMEDOUT) |
145 | err = ETIMEDOUT; |
146 | if (err == KERN_INTERRUPTED) |
147 | err = EINTR; |
148 | ret = __hurd_fail (err); |
149 | goto error; |
150 | } |
151 | |
152 | /* Token changed */ |
153 | v = atomic_load_relaxed (&isem->value); |
154 | } |
155 | } |
156 | while ((v >> SEM_VALUE_SHIFT) == 0); |
157 | } |
158 | while (!atomic_compare_exchange_weak_acquire (&isem->value, |
159 | &v, v - (1 << SEM_VALUE_SHIFT))); |
160 | |
161 | error: |
162 | pthread_cleanup_pop (0); |
163 | |
164 | __sem_wait_32_finish (isem); |
165 | #endif |
166 | |
167 | LIBC_CANCEL_RESET (cancel_oldtype); |
168 | |
169 | return ret; |
170 | } |
171 | |
172 | #if !__HAVE_64B_ATOMICS |
173 | /* Stop being a registered waiter (non-64b-atomics code only). */ |
174 | static void |
175 | __sem_wait_32_finish (struct new_sem *isem) |
176 | { |
177 | unsigned int wguess = atomic_load_relaxed (&isem->nwaiters); |
178 | if (wguess == 1) |
179 | atomic_fetch_and_acquire (&isem->value, ~SEM_NWAITERS_MASK); |
180 | |
181 | unsigned int wfinal = atomic_fetch_add_release (&isem->nwaiters, -1); |
182 | if (wfinal > 1 && wguess == 1) |
183 | { |
184 | unsigned int v = atomic_fetch_or_relaxed (&isem->value, |
185 | SEM_NWAITERS_MASK); |
186 | v >>= SEM_VALUE_SHIFT; |
187 | while (v--) |
188 | __lll_wake (&isem->value, isem->pshared ? GSYNC_SHARED : 0); |
189 | } |
190 | } |
191 | #endif |
192 | |
193 | int |
194 | __sem_clockwait (sem_t *sem, clockid_t clockid, |
195 | const struct timespec *restrict timeout) |
196 | { |
197 | return __sem_timedwait_internal (sem, clock_id: clockid, timeout); |
198 | } |
199 | weak_alias (__sem_clockwait, sem_clockwait); |
200 | |
201 | int |
202 | __sem_timedwait (sem_t *restrict sem, const struct timespec *restrict timeout) |
203 | { |
204 | return __sem_timedwait_internal (sem, CLOCK_REALTIME, timeout); |
205 | } |
206 | |
207 | weak_alias (__sem_timedwait, sem_timedwait); |
208 | |