c/pthread_extra/pthread_pause.c

   1 #define __PTHREAD_EXTRA_INTERNAL
   2
   3 #include <pthread.h>
   4 #include <pthread_extra.h>
   5 #include <signal.h>
   6 #include <semaphore.h>
   7 #include <errno.h>
   8 #include <unistd.h>
   9 #include <sys/resource.h>
  10 //#include <sys/siginfo.h>
  11 //#include <stdio.h>
  12 #include <stdlib.h>
  13 #include <assert.h>
  14 //#include <sys/time.h>
  15
  16 //Mutex that ensures proper serialization of (un)pause calls
  17 //pthread_mutex_t pthread_pause_mutex = PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP;
  18
  19 //Semaphore that ensures proper serialization of (un)pause signals
  20 sem_t pthread_pause_sem;
  21 //Once control to init the semaphore (and possibly other stuff)
  22 pthread_once_t pthread_pause_once_ctrl = PTHREAD_ONCE_INIT;
  23 void pthread_pause_once(void) {
  24         sem_init(&pthread_pause_sem, 0, 1);
  25 }
  26 void pthread_pause_init() { pthread_once(&pthread_pause_once_ctrl, &pthread_pause_once); }
  27
  28 ///When this variable is nonzero, only referenced thread is allowed to run
  29 ///Access has to be protected by pthread_user_data_lock() and pthread_pause_sem;
  30 pthread_t pthread_pause_holder = PTHREAD_XNULL;
  31
  32 void pthread_pause_handler(const int signal, siginfo_t *info, void *ptr) {
  33         (void)signal; (void)info; (void)ptr;
  34         int run = info->si_value.sival_int;
  35         //(void)td;
  36
  37         //Post semaphore to confirm that signal is handled
  38         sem_post(&pthread_pause_sem);
  39
  40         //Keep waiting for signals until we are supposed to be running
  41         if(!run) {
  42                 sigset_t sigset;
  43                 sigfillset(&sigset);
  44                 sigdelset(&sigset, PTHREAD_XSIG_STOP);
  45                 sigsuspend(&sigset);
  46         }
  47 }
  48
  49 void pthread_pause_enable() {
  50         pthread_pause_init(); //Make sure semaphore is init'd
  51
  52         //Add thread to internal registry
  53         pthread_user_data_internal(pthread_self());
  54
  55         //Nesting signals too deep is not good for stack
  56         //You can get runtime stats using following command:
  57         //grep -i sig /proc/$(pgrep binary)/status
  58         //struct rlimit sigq = {.rlim_cur = 32, .rlim_max=32};
  59         //setrlimit(RLIMIT_SIGPENDING, &sigq);
  60
  61         //Prepare signal mask
  62         sigset_t sigset;
  63         sigemptyset(&sigset);
  64         sigaddset(&sigset, PTHREAD_XSIG_STOP);
  65
  66         //Setup signal handler
  67         //signal(PTHREAD_XSIG_STOP, pthread_pause_handler);
  68         const struct sigaction pause_sa = {
  69                 .sa_sigaction = pthread_pause_handler,
  70                 .sa_mask = sigset,
  71                 .sa_flags = SA_SIGINFO | SA_RESTART,
  72                 .sa_restorer = NULL
  73         };
  74         sigaction(PTHREAD_XSIG_STOP, &pause_sa, NULL);
  75
  76         //Unblock signal
  77         pthread_sigmask(SIG_UNBLOCK, &sigset, NULL);
  78 }
  79
  80 void pthread_pause_disable() {
  81         pthread_pause_init(); //Make sure semaphore is init'd
  82
  83         //Add thread to internal registry
  84         pthread_user_data_internal(pthread_self());
  85
  86         //Block signal
  87         sigset_t sigset;
  88         sigemptyset(&sigset);
  89         sigaddset(&sigset, PTHREAD_XSIG_STOP);
  90
  91         //Make sure all signals are dispatched before we block them
  92         sem_wait(&pthread_pause_sem);
  93         pthread_sigmask(SIG_BLOCK, &sigset, NULL);
  94         sem_post(&pthread_pause_sem);
  95 }
  96
  97 /*
  98 int pthread_pause_reschedule(pthread_t thread) {
  99         //Send signal to initiate pause handler
 100         //printf("SND: %p\n", (void *)pthread_user_data_internal(thread));
 101         //while(pthread_kill(thread, PTHREAD_XSIG_STOP) == EAGAIN) usleep(1000);
 102         while(pthread_sigqueue(thread, PTHREAD_XSIG_STOP,
 103                 (const union sigval){.sival_ptr=pthread_user_data_internal(thread)}
 104                 ) == EAGAIN) usleep(1000);
 105         return 0;
 106 }
 107 */
 108
 109 int pthread_pause_reschedule(pthread_t thread) {
 110         //Decide if the thread should run and signal it
 111
 112         pthread_user_data_lock();
 113
 114         //Wait for semaphore which means signal queue is empty
 115         pthread_pause_init(); //Make sure semaphore is init'd
 116         sem_wait(&pthread_pause_sem);
 117
 118         //Only call this if you already acquired pthread_pause_sem semaphore!!!!
 119         //Otherwise call pthread_pause_reschedule()
 120
 121         //Check if thread has running flag
 122         int run = (pthread_user_data_internal(thread)->running);
 123         //Check if privileged (single thread) mode is active
 124         if(!pthread_equal(pthread_pause_holder, PTHREAD_XNULL) && !pthread_equal(pthread_pause_holder, thread)) {
 125                 run = 0;
 126         }
 127
 128         //Send signal to initiate pause handler (keep trying while SigQueue is full)
 129         //while(pthread_kill(thread, PTHREAD_XSIG_STOP) == EAGAIN) usleep(1000);
 130         //printf("Sched %lu = %d (self: %lu, lck: %lu)\n", thread, run, pthread_self(), pthread_pause_holder);
 131         while(pthread_sigqueue(thread, PTHREAD_XSIG_STOP,
 132                 (const union sigval){.sival_int=run}
 133                 ) == EAGAIN) usleep(1000);
 134
 135         //Wait for signal to be delivered
 136         sem_wait(&pthread_pause_sem);
 137         sem_post(&pthread_pause_sem);
 138         pthread_user_data_unlock();
 139
 140         return 0;
 141 }
 142
 143 int pthread_extra_yield() {
 144         //Yield to both schedulers
 145         pthread_pause_reschedule(pthread_self());
 146         return pthread_yield();
 147 }
 148
 149 int pthread_pause(pthread_t thread) {
 150         //Set thread as paused and notify it via signal (wait when queue full)
 151         pthread_user_data_lock();
 152         pthread_user_data_internal(thread)->running = 0;
 153         pthread_pause_reschedule(thread);
 154         pthread_user_data_unlock();
 155         return 0;
 156 }
 157
 158 int pthread_unpause(pthread_t thread) {
 159         //Set thread as running and notify it via signal (wait when queue full)
 160         pthread_user_data_lock();
 161         pthread_user_data_internal(thread)->running = 1;
 162         pthread_pause_reschedule(thread);
 163         pthread_user_data_unlock();
 164         return 0;
 165 }
 166
 167 ///Enter exclusive mode by pausing everyone else
 168 int pthread_pause_all() {
 169         //printf("Pause ALL\n");
 170         pthread_user_data_lock();
 171         //printf("Pause ALL+\n");
 172         //printf("Pause %p == %p\n", (void *)pthread_pause_holder, (void *)pthread_self());
 173         if(!pthread_equal(pthread_pause_holder,PTHREAD_XNULL)) assert(pthread_equal(pthread_pause_holder, pthread_self()));
 174         pthread_pause_holder = pthread_self();
 175         pthread_user_data_internal_iterate(&pthread_pause_reschedule, NULL);
 176         //printf("Pause ALL!\n");
 177         pthread_user_data_unlock();
 178         return 0;
 179 }
 180
 181 ///Leave exclusive mode by unpausing everyone else
 182 int pthread_unpause_all() {
 183         //printf("UnPause ALL\n");
 184         pthread_user_data_lock();
 185         //printf("UnPause ALL+\n");
 186         if(!pthread_equal(pthread_pause_holder,PTHREAD_XNULL)) assert(pthread_equal(pthread_pause_holder, pthread_self()));
 187         pthread_pause_holder = PTHREAD_XNULL;
 188         pthread_user_data_internal_iterate(&pthread_pause_reschedule, NULL);
 189         //printf("UnPause ALL!\n");
 190         pthread_user_data_unlock();
 191         return 0;
 192 }
 193
 194
 195 // Wrappers ///////////////////////////////////////////////////////////
 196
 197
 198 typedef struct pthread_extra_wrapper_t {
 199         void *(*start_routine)(void *);
 200         void *restrict arg;
 201 } pthread_extra_wrapper_t;
 202
 203 void *pthread_extra_thread_wrapper(void *arg) {
 204         pthread_extra_wrapper_t task = *((pthread_extra_wrapper_t*)arg);
 205         free(arg);
 206
 207         //Register new thread to user data structure
 208         pthread_user_data_internal(pthread_self()); //Perhaps already done in pthread_extra_yield()??
 209
 210         //TODO: user_data should do this automaticaly?
 211         pthread_cleanup_push(pthread_user_data_cleanup, (void *)pthread_self());
 212
 213         //Check if we should be running according to pthread_pause sub-scheduler
 214         //pthread_pause_reschedule(pthread_self());
 215         pthread_extra_yield();
 216
 217         //Run actual task
 218         return task.start_routine(task.arg);
 219
 220         pthread_cleanup_pop(1); //Needed by pthread_cleanup_push() macro
 221 }
 222
 223 int pthread_extra_create(pthread_t *restrict thread,
 224                           const pthread_attr_t *restrict attr,
 225                           void *(*start_routine)(void *),
 226                           void *restrict arg) {
 227
 228         pthread_extra_wrapper_t *task = malloc(sizeof(pthread_extra_wrapper_t));
 229         assert(task != NULL);
 230         task->start_routine=start_routine;
 231         task->arg=arg;
 232         return pthread_create(thread, attr, pthread_extra_thread_wrapper, task);
 233 }