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 // System calls.
38 extern "C" int __rt_sigprocmask(int, const sigset64_t*, sigset64_t*, size_t);
39 extern "C" int __rt_sigtimedwait(const sigset64_t*, siginfo_t*, const timespec*, size_t);
40 extern "C" int __timer_create(clockid_t, sigevent*, __kernel_timer_t*);
41 extern "C" int __timer_delete(__kernel_timer_t);
42 extern "C" int __timer_getoverrun(__kernel_timer_t);
43 extern "C" int __timer_gettime(__kernel_timer_t, itimerspec*);
44 extern "C" int __timer_settime(__kernel_timer_t, int, const itimerspec*, itimerspec*);
45
46 // Most POSIX timers are handled directly by the kernel. We translate SIGEV_THREAD timers
47 // into SIGEV_THREAD_ID timers so the kernel handles all the time-related stuff and we just
48 // need to worry about running user code on a thread.
49
50 // We can't use SIGALRM because too many other C library functions throw that around, and since
51 // they don't send to a specific thread, all threads are eligible to handle the signal and we can
52 // end up with one of our POSIX timer threads handling it (meaning that the intended recipient
53 // doesn't). glibc uses SIGRTMIN for its POSIX timer implementation, so in the absence of any
54 // reason to use anything else, we use that too.
55 static const int TIMER_SIGNAL = (__SIGRTMIN + 0);
56
57 struct PosixTimer {
58 __kernel_timer_t kernel_timer_id;
59
60 int sigev_notify;
61
62 // The fields below are only needed for a SIGEV_THREAD timer.
63 pthread_t callback_thread;
64 void (*callback)(sigval_t);
65 sigval_t callback_argument;
66 atomic_bool deleted; // Set when the timer is deleted, to prevent further calling of callback.
67 };
68
to_kernel_timer_id(timer_t timer)69 static __kernel_timer_t to_kernel_timer_id(timer_t timer) {
70 return reinterpret_cast<PosixTimer*>(timer)->kernel_timer_id;
71 }
72
__timer_thread_start(void * arg)73 static void* __timer_thread_start(void* arg) {
74 PosixTimer* timer = reinterpret_cast<PosixTimer*>(arg);
75
76 sigset64_t sigset = {};
77 sigaddset64(&sigset, TIMER_SIGNAL);
78
79 while (true) {
80 // Wait for a signal...
81 siginfo_t si = {};
82 if (__rt_sigtimedwait(&sigset, &si, nullptr, sizeof(sigset)) == -1) continue;
83
84 if (si.si_code == SI_TIMER) {
85 // This signal was sent because a timer fired, so call the callback.
86
87 // All events to the callback will be ignored when the timer is deleted.
88 if (atomic_load(&timer->deleted) == true) {
89 continue;
90 }
91 timer->callback(timer->callback_argument);
92 } else if (si.si_code == SI_TKILL) {
93 // This signal was sent because someone wants us to exit.
94 free(timer);
95 return nullptr;
96 }
97 }
98 }
99
__timer_thread_stop(PosixTimer * timer)100 static void __timer_thread_stop(PosixTimer* timer) {
101 atomic_store(&timer->deleted, true);
102 pthread_kill(timer->callback_thread, TIMER_SIGNAL);
103 }
104
105 // http://pubs.opengroup.org/onlinepubs/9699919799/functions/timer_create.html
timer_create(clockid_t clock_id,sigevent * evp,timer_t * timer_id)106 int timer_create(clockid_t clock_id, sigevent* evp, timer_t* timer_id) {
107 PosixTimer* timer = reinterpret_cast<PosixTimer*>(malloc(sizeof(PosixTimer)));
108 if (timer == nullptr) {
109 return -1;
110 }
111
112 timer->sigev_notify = (evp == nullptr) ? SIGEV_SIGNAL : evp->sigev_notify;
113
114 // If not a SIGEV_THREAD timer, the kernel can handle it without our help.
115 if (timer->sigev_notify != SIGEV_THREAD) {
116 if (__timer_create(clock_id, evp, &timer->kernel_timer_id) == -1) {
117 free(timer);
118 return -1;
119 }
120
121 *timer_id = timer;
122 return 0;
123 }
124
125 // Otherwise, this must be SIGEV_THREAD timer...
126 timer->callback = evp->sigev_notify_function;
127 timer->callback_argument = evp->sigev_value;
128 atomic_init(&timer->deleted, false);
129
130 // Check arguments that the kernel doesn't care about but we do.
131 if (timer->callback == nullptr) {
132 free(timer);
133 errno = EINVAL;
134 return -1;
135 }
136
137 // Create this timer's thread.
138 pthread_attr_t thread_attributes;
139 if (evp->sigev_notify_attributes == nullptr) {
140 pthread_attr_init(&thread_attributes);
141 } else {
142 thread_attributes = *reinterpret_cast<pthread_attr_t*>(evp->sigev_notify_attributes);
143 }
144 pthread_attr_setdetachstate(&thread_attributes, PTHREAD_CREATE_DETACHED);
145
146 // We start the thread with TIMER_SIGNAL blocked by blocking the signal here and letting it
147 // inherit. If it tried to block the signal itself, there would be a race.
148 sigset64_t sigset = {};
149 sigaddset64(&sigset, TIMER_SIGNAL);
150 sigset64_t old_sigset;
151
152 // Use __rt_sigprocmask instead of sigprocmask64 to avoid filtering out TIMER_SIGNAL.
153 __rt_sigprocmask(SIG_BLOCK, &sigset, &old_sigset, sizeof(sigset));
154
155 int rc = pthread_create(&timer->callback_thread, &thread_attributes, __timer_thread_start, timer);
156
157 __rt_sigprocmask(SIG_SETMASK, &old_sigset, nullptr, sizeof(old_sigset));
158
159 if (rc != 0) {
160 free(timer);
161 errno = rc;
162 return -1;
163 }
164
165 sigevent se = *evp;
166 se.sigev_signo = TIMER_SIGNAL;
167 se.sigev_notify = SIGEV_THREAD_ID;
168 se.sigev_notify_thread_id = pthread_gettid_np(timer->callback_thread);
169 if (__timer_create(clock_id, &se, &timer->kernel_timer_id) == -1) {
170 __timer_thread_stop(timer);
171 return -1;
172 }
173
174 // Give the thread a specific meaningful name.
175 // It can't do this itself because the kernel timer isn't created until after it's running.
176 char name[16]; // 16 is the kernel-imposed limit.
177 snprintf(name, sizeof(name), "POSIX timer %d", to_kernel_timer_id(timer));
178 pthread_setname_np(timer->callback_thread, name);
179
180 *timer_id = timer;
181 return 0;
182 }
183
184 // http://pubs.opengroup.org/onlinepubs/9699919799/functions/timer_delete.html
timer_delete(timer_t id)185 int timer_delete(timer_t id) {
186 int rc = __timer_delete(to_kernel_timer_id(id));
187 if (rc == -1) {
188 return -1;
189 }
190
191 PosixTimer* timer = reinterpret_cast<PosixTimer*>(id);
192 if (timer->sigev_notify == SIGEV_THREAD) {
193 // Stopping the timer's thread frees the timer data when it's safe.
194 __timer_thread_stop(timer);
195 } else {
196 // For timers without threads, we can just free right away.
197 free(timer);
198 }
199
200 return 0;
201 }
202
203 // http://pubs.opengroup.org/onlinepubs/9699919799/functions/timer_gettime.html
timer_gettime(timer_t id,itimerspec * ts)204 int timer_gettime(timer_t id, itimerspec* ts) {
205 return __timer_gettime(to_kernel_timer_id(id), ts);
206 }
207
208 // http://pubs.opengroup.org/onlinepubs/9699919799/functions/timer_settime.html
209 // When using timer_settime to disarm a repeatable SIGEV_THREAD timer with a very small
210 // period (like below 1ms), the kernel may continue to send events to the callback thread
211 // for a few extra times. This behavior is fine because in POSIX standard: The effect of
212 // disarming or resetting a timer with pending expiration notifications is unspecified.
timer_settime(timer_t id,int flags,const itimerspec * ts,itimerspec * ots)213 int timer_settime(timer_t id, int flags, const itimerspec* ts, itimerspec* ots) {
214 PosixTimer* timer= reinterpret_cast<PosixTimer*>(id);
215 return __timer_settime(timer->kernel_timer_id, flags, ts, ots);
216 }
217
218 // http://pubs.opengroup.org/onlinepubs/9699919799/functions/timer_getoverrun.html
timer_getoverrun(timer_t id)219 int timer_getoverrun(timer_t id) {
220 return __timer_getoverrun(to_kernel_timer_id(id));
221 }
222