1 /*
2 * Copyright (C) 2008 The Android Open Source Project
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * * Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * * Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in
12 * the documentation and/or other materials provided with the
13 * distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
16 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
17 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
18 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
19 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
21 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
22 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
23 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
24 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
25 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 * SUCH DAMAGE.
27 */
28
29 #include <errno.h>
30 #include <malloc.h>
31 #include <pthread.h>
32 #include <stdatomic.h>
33 #include <stdio.h>
34 #include <string.h>
35 #include <time.h>
36
37 #include "private/bionic_lock.h"
38
39 // System calls.
40 extern "C" int __rt_sigprocmask(int, const sigset64_t*, sigset64_t*, size_t);
41 extern "C" int __rt_sigtimedwait(const sigset64_t*, siginfo_t*, const timespec*, size_t);
42 extern "C" int __timer_create(clockid_t, sigevent*, __kernel_timer_t*);
43 extern "C" int __timer_delete(__kernel_timer_t);
44 extern "C" int __timer_getoverrun(__kernel_timer_t);
45 extern "C" int __timer_gettime(__kernel_timer_t, itimerspec*);
46 extern "C" int __timer_settime(__kernel_timer_t, int, const itimerspec*, itimerspec*);
47
48 // Most POSIX timers are handled directly by the kernel. We translate SIGEV_THREAD timers
49 // into SIGEV_THREAD_ID timers so the kernel handles all the time-related stuff and we just
50 // need to worry about running user code on a thread.
51
52 // We can't use SIGALRM because too many other C library functions throw that around, and since
53 // they don't send to a specific thread, all threads are eligible to handle the signal and we can
54 // end up with one of our POSIX timer threads handling it (meaning that the intended recipient
55 // doesn't). glibc uses SIGRTMIN for its POSIX timer implementation, so in the absence of any
56 // reason to use anything else, we use that too.
57 static const int TIMER_SIGNAL = (__SIGRTMIN + 0);
58
59 struct PosixTimer {
60 __kernel_timer_t kernel_timer_id;
61
62 int sigev_notify;
63
64 // The fields below are only needed for a SIGEV_THREAD timer.
65 Lock startup_handshake_lock;
66 pthread_t callback_thread;
67 void (*callback)(sigval_t);
68 sigval_t callback_argument;
69 atomic_bool deleted; // Set when the timer is deleted, to prevent further calling of callback.
70 };
71
to_kernel_timer_id(timer_t timer)72 static __kernel_timer_t to_kernel_timer_id(timer_t timer) {
73 return reinterpret_cast<PosixTimer*>(timer)->kernel_timer_id;
74 }
75
__timer_thread_start(void * arg)76 static void* __timer_thread_start(void* arg) {
77 PosixTimer* timer = reinterpret_cast<PosixTimer*>(arg);
78
79 // Check that our parent managed to create the kernel timer and bail if not...
80 timer->startup_handshake_lock.lock();
81 if (timer->kernel_timer_id == -1) {
82 free(timer);
83 return nullptr;
84 }
85
86 // Give ourselves a specific meaningful name now we have a kernel timer.
87 char name[16]; // 16 is the kernel-imposed limit.
88 snprintf(name, sizeof(name), "POSIX timer %d", to_kernel_timer_id(timer));
89 pthread_setname_np(timer->callback_thread, name);
90
91 sigset64_t sigset = {};
92 sigaddset64(&sigset, TIMER_SIGNAL);
93
94 while (true) {
95 // Wait for a signal...
96 siginfo_t si = {};
97 if (__rt_sigtimedwait(&sigset, &si, nullptr, sizeof(sigset)) == -1) continue;
98
99 if (si.si_code == SI_TIMER) {
100 // This signal was sent because a timer fired, so call the callback.
101
102 // All events to the callback will be ignored when the timer is deleted.
103 if (atomic_load(&timer->deleted) == true) {
104 continue;
105 }
106 timer->callback(timer->callback_argument);
107 } else if (si.si_code == SI_TKILL) {
108 // This signal was sent because someone wants us to exit.
109 free(timer);
110 return nullptr;
111 }
112 }
113 }
114
__timer_thread_stop(PosixTimer * timer)115 static void __timer_thread_stop(PosixTimer* timer) {
116 atomic_store(&timer->deleted, true);
117 pthread_kill(timer->callback_thread, TIMER_SIGNAL);
118 }
119
120 // http://pubs.opengroup.org/onlinepubs/9699919799/functions/timer_create.html
timer_create(clockid_t clock_id,sigevent * evp,timer_t * timer_id)121 int timer_create(clockid_t clock_id, sigevent* evp, timer_t* timer_id) {
122 PosixTimer* timer = reinterpret_cast<PosixTimer*>(malloc(sizeof(PosixTimer)));
123 if (timer == nullptr) {
124 return -1;
125 }
126
127 timer->kernel_timer_id = -1;
128 timer->sigev_notify = (evp == nullptr) ? SIGEV_SIGNAL : evp->sigev_notify;
129
130 // If not a SIGEV_THREAD timer, the kernel can handle it without our help.
131 if (timer->sigev_notify != SIGEV_THREAD) {
132 if (__timer_create(clock_id, evp, &timer->kernel_timer_id) == -1) {
133 free(timer);
134 return -1;
135 }
136
137 *timer_id = timer;
138 return 0;
139 }
140
141 // Otherwise, this must be SIGEV_THREAD timer...
142 timer->callback = evp->sigev_notify_function;
143 timer->callback_argument = evp->sigev_value;
144 atomic_init(&timer->deleted, false);
145
146 // Check arguments that the kernel doesn't care about but we do.
147 if (timer->callback == nullptr) {
148 free(timer);
149 errno = EINVAL;
150 return -1;
151 }
152
153 // Create this timer's thread.
154 pthread_attr_t thread_attributes;
155 if (evp->sigev_notify_attributes == nullptr) {
156 pthread_attr_init(&thread_attributes);
157 } else {
158 thread_attributes = *reinterpret_cast<pthread_attr_t*>(evp->sigev_notify_attributes);
159 }
160 pthread_attr_setdetachstate(&thread_attributes, PTHREAD_CREATE_DETACHED);
161
162 // We start the thread with TIMER_SIGNAL blocked by blocking the signal here and letting it
163 // inherit. If it tried to block the signal itself, there would be a race.
164 sigset64_t sigset = {};
165 sigaddset64(&sigset, TIMER_SIGNAL);
166 sigset64_t old_sigset;
167
168 // Prevent the child thread from running until the timer has been created.
169 timer->startup_handshake_lock.init(false);
170 timer->startup_handshake_lock.lock();
171
172 // Use __rt_sigprocmask instead of sigprocmask64 to avoid filtering out TIMER_SIGNAL.
173 __rt_sigprocmask(SIG_BLOCK, &sigset, &old_sigset, sizeof(sigset));
174
175 int rc = pthread_create(&timer->callback_thread, &thread_attributes, __timer_thread_start, timer);
176
177 __rt_sigprocmask(SIG_SETMASK, &old_sigset, nullptr, sizeof(old_sigset));
178
179 if (rc != 0) {
180 free(timer);
181 errno = rc;
182 return -1;
183 }
184
185 // Try to create the kernel timer.
186 sigevent se = *evp;
187 se.sigev_signo = TIMER_SIGNAL;
188 se.sigev_notify = SIGEV_THREAD_ID;
189 se.sigev_notify_thread_id = pthread_gettid_np(timer->callback_thread);
190 rc = __timer_create(clock_id, &se, &timer->kernel_timer_id);
191
192 // Let the child run (whether we created the kernel timer or not).
193 timer->startup_handshake_lock.unlock();
194 // If __timer_create(2) failed, the child will kill itself and free the
195 // timer struct, so we just need to exit.
196 if (rc == -1) {
197 return -1;
198 }
199
200 *timer_id = timer;
201 return 0;
202 }
203
204 // http://pubs.opengroup.org/onlinepubs/9699919799/functions/timer_delete.html
timer_delete(timer_t id)205 int timer_delete(timer_t id) {
206 int rc = __timer_delete(to_kernel_timer_id(id));
207 if (rc == -1) {
208 return -1;
209 }
210
211 PosixTimer* timer = reinterpret_cast<PosixTimer*>(id);
212 if (timer->sigev_notify == SIGEV_THREAD) {
213 // Stopping the timer's thread frees the timer data when it's safe.
214 __timer_thread_stop(timer);
215 } else {
216 // For timers without threads, we can just free right away.
217 free(timer);
218 }
219
220 return 0;
221 }
222
223 // http://pubs.opengroup.org/onlinepubs/9699919799/functions/timer_gettime.html
timer_gettime(timer_t id,itimerspec * ts)224 int timer_gettime(timer_t id, itimerspec* ts) {
225 return __timer_gettime(to_kernel_timer_id(id), ts);
226 }
227
228 // http://pubs.opengroup.org/onlinepubs/9699919799/functions/timer_settime.html
229 // When using timer_settime to disarm a repeatable SIGEV_THREAD timer with a very small
230 // period (like below 1ms), the kernel may continue to send events to the callback thread
231 // for a few extra times. This behavior is fine because in POSIX standard: The effect of
232 // disarming or resetting a timer with pending expiration notifications is unspecified.
timer_settime(timer_t id,int flags,const itimerspec * ts,itimerspec * ots)233 int timer_settime(timer_t id, int flags, const itimerspec* ts, itimerspec* ots) {
234 PosixTimer* timer= reinterpret_cast<PosixTimer*>(id);
235 return __timer_settime(timer->kernel_timer_id, flags, ts, ots);
236 }
237
238 // http://pubs.opengroup.org/onlinepubs/9699919799/functions/timer_getoverrun.html
timer_getoverrun(timer_t id)239 int timer_getoverrun(timer_t id) {
240 return __timer_getoverrun(to_kernel_timer_id(id));
241 }
242