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      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.
     38 extern "C" int __rt_sigtimedwait(const sigset_t*, siginfo_t*, const struct timespec*, size_t);
     39 extern "C" int __timer_create(clockid_t, sigevent*, __kernel_timer_t*);
     40 extern "C" int __timer_delete(__kernel_timer_t);
     41 extern "C" int __timer_getoverrun(__kernel_timer_t);
     42 extern "C" int __timer_gettime(__kernel_timer_t, itimerspec*);
     43 extern "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.
     54 static const int TIMER_SIGNAL = (__SIGRTMIN + 0);
     55 
     56 struct 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 
     68 static __kernel_timer_t to_kernel_timer_id(timer_t timer) {
     69   return reinterpret_cast<PosixTimer*>(timer)->kernel_timer_id;
     70 }
     71 
     72 static 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 
     98 static 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
    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 == 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
    183 int 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
    202 int 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
    207 int 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
    223 int timer_getoverrun(timer_t id) {
    224   return __timer_getoverrun(to_kernel_timer_id(id));
    225 }
    226