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 "pthread_internal.h"
30#include "private/bionic_futex.h"
31#include "private/kernel_sigset_t.h"
32
33#include <errno.h>
34#include <stdio.h>
35#include <string.h>
36
37// System calls.
38extern "C" int __rt_sigtimedwait(const sigset_t*, siginfo_t*, const struct timespec*, size_t);
39extern "C" int __timer_create(clockid_t, sigevent*, __kernel_timer_t*);
40extern "C" int __timer_delete(__kernel_timer_t);
41extern "C" int __timer_getoverrun(__kernel_timer_t);
42extern "C" int __timer_gettime(__kernel_timer_t, itimerspec*);
43extern "C" int __timer_settime(__kernel_timer_t, int, const itimerspec*, itimerspec*);
44
45// Most POSIX timers are handled directly by the kernel. We translate SIGEV_THREAD timers
46// into SIGEV_THREAD_ID timers so the kernel handles all the time-related stuff and we just
47// need to worry about running user code on a thread.
48
49// We can't use SIGALRM because too many other C library functions throw that around, and since
50// they don't send to a specific thread, all threads are eligible to handle the signal and we can
51// end up with one of our POSIX timer threads handling it (meaning that the intended recipient
52// doesn't). glibc uses SIGRTMIN for its POSIX timer implementation, so in the absence of any
53// reason to use anything else, we use that too.
54static const int TIMER_SIGNAL = (__SIGRTMIN + 0);
55
56struct PosixTimer {
57  __kernel_timer_t kernel_timer_id;
58
59  int sigev_notify;
60
61  // These fields are only needed for a SIGEV_THREAD timer.
62  pthread_t callback_thread;
63  void (*callback)(sigval_t);
64  sigval_t callback_argument;
65  volatile bool armed;
66};
67
68static __kernel_timer_t to_kernel_timer_id(timer_t timer) {
69  return reinterpret_cast<PosixTimer*>(timer)->kernel_timer_id;
70}
71
72static void* __timer_thread_start(void* arg) {
73  PosixTimer* timer = reinterpret_cast<PosixTimer*>(arg);
74
75  kernel_sigset_t sigset;
76  sigaddset(sigset.get(), TIMER_SIGNAL);
77
78  while (true) {
79    // Wait for a signal...
80    siginfo_t si;
81    memset(&si, 0, sizeof(si));
82    int rc = __rt_sigtimedwait(sigset.get(), &si, NULL, sizeof(sigset));
83    if (rc == -1) {
84      continue;
85    }
86
87    if (si.si_code == SI_TIMER && timer->armed) {
88      // This signal was sent because a timer fired, so call the callback.
89      timer->callback(timer->callback_argument);
90    } else if (si.si_code == SI_TKILL) {
91      // This signal was sent because someone wants us to exit.
92      free(timer);
93      return NULL;
94    }
95  }
96}
97
98static void __timer_thread_stop(PosixTimer* timer) {
99  // Immediately mark the timer as disarmed so even if some events
100  // continue to happen, the callback won't be called.
101  timer->armed = false;
102  pthread_kill(timer->callback_thread, TIMER_SIGNAL);
103}
104
105// http://pubs.opengroup.org/onlinepubs/9699919799/functions/timer_create.html
106int timer_create(clockid_t clock_id, sigevent* evp, timer_t* timer_id) {
107  PosixTimer* timer = reinterpret_cast<PosixTimer*>(malloc(sizeof(PosixTimer)));
108  if (timer == NULL) {
109    return -1;
110  }
111
112  timer->sigev_notify = (evp == NULL) ? 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  timer->armed = false;
129
130  // Check arguments that the kernel doesn't care about but we do.
131  if (timer->callback == NULL) {
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 == NULL) {
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  kernel_sigset_t sigset;
149  sigaddset(sigset.get(), TIMER_SIGNAL);
150  kernel_sigset_t old_sigset;
151  pthread_sigmask(SIG_BLOCK, sigset.get(), old_sigset.get());
152
153  int rc = pthread_create(&timer->callback_thread, &thread_attributes, __timer_thread_start, timer);
154
155  pthread_sigmask(SIG_SETMASK, old_sigset.get(), NULL);
156
157  if (rc != 0) {
158    free(timer);
159    errno = rc;
160    return -1;
161  }
162
163  sigevent se = *evp;
164  se.sigev_signo = TIMER_SIGNAL;
165  se.sigev_notify = SIGEV_THREAD_ID;
166  se.sigev_notify_thread_id = pthread_gettid_np(timer->callback_thread);
167  if (__timer_create(clock_id, &se, &timer->kernel_timer_id) == -1) {
168    __timer_thread_stop(timer);
169    return -1;
170  }
171
172  // Give the thread a meaningful name.
173  // It can't do this itself because the kernel timer isn't created until after it's running.
174  char name[32];
175  snprintf(name, sizeof(name), "POSIX interval timer %d", to_kernel_timer_id(timer));
176  pthread_setname_np(timer->callback_thread, name);
177
178  *timer_id = timer;
179  return 0;
180}
181
182// http://pubs.opengroup.org/onlinepubs/9699919799/functions/timer_delete.html
183int timer_delete(timer_t id) {
184  int rc = __timer_delete(to_kernel_timer_id(id));
185  if (rc == -1) {
186    return -1;
187  }
188
189  PosixTimer* timer = reinterpret_cast<PosixTimer*>(id);
190  if (timer->sigev_notify == SIGEV_THREAD) {
191    // Stopping the timer's thread frees the timer data when it's safe.
192    __timer_thread_stop(timer);
193  } else {
194    // For timers without threads, we can just free right away.
195    free(timer);
196  }
197
198  return 0;
199}
200
201// http://pubs.opengroup.org/onlinepubs/9699919799/functions/timer_getoverrun.html
202int timer_gettime(timer_t id, itimerspec* ts) {
203  return __timer_gettime(to_kernel_timer_id(id), ts);
204}
205
206// http://pubs.opengroup.org/onlinepubs/9699919799/functions/timer_getoverrun.html
207int timer_settime(timer_t id, int flags, const itimerspec* ts, itimerspec* ots) {
208  PosixTimer* timer= reinterpret_cast<PosixTimer*>(id);
209  int rc = __timer_settime(timer->kernel_timer_id, flags, ts, ots);
210  if (rc == 0) {
211    // Mark the timer as either being armed or disarmed. This avoids the
212    // callback being called after the disarm for SIGEV_THREAD timers only.
213    if (ts->it_value.tv_sec != 0 || ts->it_value.tv_nsec != 0) {
214      timer->armed = true;
215    } else {
216      timer->armed = false;
217    }
218  }
219  return rc;
220}
221
222// http://pubs.opengroup.org/onlinepubs/9699919799/functions/timer_getoverrun.html
223int timer_getoverrun(timer_t id) {
224  return __timer_getoverrun(to_kernel_timer_id(id));
225}
226