1 | /* pthread_hurd_cond_timedwait_np. Hurd-specific wait on a condition. |
2 | Copyright (C) 2012-2024 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 <hurd/signal.h> |
22 | #include <time.h> |
23 | |
24 | #include <pt-internal.h> |
25 | |
26 | extern int __pthread_hurd_cond_timedwait_internal (pthread_cond_t *cond, |
27 | pthread_mutex_t *mutex, |
28 | const struct timespec |
29 | *abstime); |
30 | |
31 | int |
32 | __pthread_hurd_cond_timedwait_np (pthread_cond_t *cond, |
33 | pthread_mutex_t *mutex, |
34 | const struct timespec *abstime) |
35 | { |
36 | return __pthread_hurd_cond_timedwait_internal (cond, mutex, abstime); |
37 | } |
38 | |
39 | strong_alias (__pthread_hurd_cond_timedwait_np, pthread_hurd_cond_timedwait_np); |
40 | |
41 | int |
42 | __pthread_hurd_cond_timedwait_internal (pthread_cond_t *cond, |
43 | pthread_mutex_t *mutex, |
44 | const struct timespec *abstime) |
45 | { |
46 | struct hurd_sigstate *ss = _hurd_self_sigstate (); |
47 | struct __pthread *self = _pthread_self (); |
48 | error_t err = 0; |
49 | int cancel, drain; |
50 | clockid_t clock_id = __pthread_default_condattr.__clock; |
51 | |
52 | /* This function will be called by hurd_thread_cancel while we are blocked |
53 | We wake up our thread if it's still blocking or about to block, so it will |
54 | progress and notice the cancellation flag. */ |
55 | void cancel_me (void) |
56 | { |
57 | int unblock; |
58 | |
59 | __pthread_spin_wait (&cond->__lock); |
60 | /* The thread only needs to be awaken if it's blocking or about to block. |
61 | If it was already unblocked, it's not queued any more. */ |
62 | unblock = self->prevp != NULL; |
63 | if (unblock) |
64 | __pthread_dequeue (self); |
65 | __pthread_spin_unlock (&cond->__lock); |
66 | |
67 | if (unblock) |
68 | __pthread_wakeup (self); |
69 | } |
70 | |
71 | assert (ss->intr_port == MACH_PORT_NULL); /* Sanity check for signal bugs. */ |
72 | |
73 | if (abstime != NULL && ! valid_nanoseconds (ns: abstime->tv_nsec)) |
74 | return EINVAL; |
75 | |
76 | err = __pthread_mutex_checklocked (mutex); |
77 | if (err) |
78 | return err; |
79 | |
80 | /* Atomically enqueue our thread on the condition variable's queue of |
81 | waiters, and mark our sigstate to indicate that `cancel_me' must be |
82 | called to wake us up. We must hold the sigstate lock while acquiring |
83 | the condition variable's lock and tweaking it, so that |
84 | hurd_thread_cancel can never suspend us and then deadlock waiting for |
85 | the condition variable's lock. */ |
86 | |
87 | __spin_lock (&ss->lock); |
88 | __pthread_spin_wait (&cond->__lock); |
89 | cancel = ss->cancel; |
90 | if (cancel) |
91 | /* We were cancelled before doing anything. Don't block at all. */ |
92 | ss->cancel = 0; |
93 | else |
94 | { |
95 | /* Put us on the queue so that pthread_cond_broadcast will know to wake |
96 | us up. */ |
97 | __pthread_enqueue (&cond->__queue, self); |
98 | if (cond->__attr) |
99 | clock_id = cond->__attr->__clock; |
100 | /* Tell hurd_thread_cancel how to unblock us. */ |
101 | ss->cancel_hook = &cancel_me; |
102 | } |
103 | __pthread_spin_unlock (&cond->__lock); |
104 | __spin_unlock (&ss->lock); |
105 | |
106 | /* Increase the waiter reference count. Relaxed MO is sufficient because |
107 | we only need to synchronize when decrementing the reference count. |
108 | We however need to have the mutex held to prevent concurrency with |
109 | a pthread_cond_destroy. */ |
110 | atomic_fetch_add_relaxed (&cond->__wrefs, 2); |
111 | |
112 | if (cancel) |
113 | { |
114 | /* Cancelled on entry. Just leave the mutex locked. */ |
115 | mutex = NULL; |
116 | |
117 | __spin_lock (&ss->lock); |
118 | } |
119 | else |
120 | { |
121 | /* Release MUTEX before blocking. */ |
122 | __pthread_mutex_unlock (mutex); |
123 | |
124 | /* Block the thread. */ |
125 | if (abstime != NULL) |
126 | err = __pthread_timedblock (self, abstime, clock_id); |
127 | else |
128 | { |
129 | err = 0; |
130 | __pthread_block (self); |
131 | } |
132 | |
133 | /* As it was done when enqueueing, prevent hurd_thread_cancel from |
134 | suspending us while the condition lock is held. */ |
135 | __spin_lock (&ss->lock); |
136 | __pthread_spin_wait (&cond->__lock); |
137 | if (self->prevp == NULL) |
138 | /* Another thread removed us from the list of waiters, which means |
139 | a wakeup message has been sent. It was either consumed while |
140 | we were blocking, or queued after we timed out and before we |
141 | acquired the condition lock, in which case the message queue |
142 | must be drained. */ |
143 | drain = err ? 1 : 0; |
144 | else |
145 | { |
146 | /* We're still in the list of waiters. No one attempted to wake us |
147 | up, i.e. we timed out. */ |
148 | __pthread_dequeue (self); |
149 | drain = 0; |
150 | } |
151 | __pthread_spin_unlock (&cond->__lock); |
152 | |
153 | if (drain) |
154 | __pthread_block (self); |
155 | } |
156 | |
157 | /* If destruction is pending (i.e., the wake-request flag is nonzero) and we |
158 | are the last waiter (prior value of __wrefs was 1 << 1), then wake any |
159 | threads waiting in pthread_cond_destroy. Release MO to synchronize with |
160 | these threads. Don't bother clearing the wake-up request flag. */ |
161 | if ((atomic_fetch_add_release (&cond->__wrefs, -2)) == 3) |
162 | __gsync_wake (__mach_task_self (), (vm_offset_t) &cond->__wrefs, 0, 0); |
163 | |
164 | /* Clear the hook, now that we are done blocking. */ |
165 | ss->cancel_hook = NULL; |
166 | /* Check the cancellation flag; we might have unblocked due to |
167 | cancellation rather than a normal pthread_cond_signal or |
168 | pthread_cond_broadcast (or we might have just happened to get cancelled |
169 | right after waking up). */ |
170 | cancel |= ss->cancel; |
171 | ss->cancel = 0; |
172 | __spin_unlock (&ss->lock); |
173 | |
174 | if (mutex != NULL) |
175 | /* Reacquire the mutex and return. */ |
176 | __pthread_mutex_lock (mutex); |
177 | |
178 | if (cancel) |
179 | return EINTR; |
180 | else if (err) |
181 | { |
182 | assert (err == ETIMEDOUT); |
183 | return err; |
184 | } |
185 | |
186 | return 0; |
187 | } |
188 | |