/* http://cygwin.com/ml/cygwin/2012-05/msg00434.html */

#include <errno.h>
#include <pthread.h>
#include <semaphore.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

pthread_t tids[3];
sem_t semaphore;

static void cleanup_handler(void *arg) {
  int *intptr = (int*)arg;
  pthread_t self = pthread_self();
  fprintf(stderr, "Thread %i exiting (%p)\n", *intptr, self);
}

static void* simplethread(void *arg) {
  int *intptr = (int*)arg;
  pthread_t self = pthread_self();
  fprintf(stderr, "Thread %i starting (%p)\n", *intptr, self);

  pthread_cleanup_push(&cleanup_handler, intptr);

  while (1) {
    if (sem_wait(&semaphore) != 0) {
      fprintf(stderr, "Thread %i encountered an error: %s (%p)\n",
          *intptr, strerror(errno), self);
    } else {
      fprintf(stderr, "Thread %i woke up just fine\n", *intptr);
    }
  }

  pthread_cleanup_pop(1);
  return NULL;
}

static void sigusr1_handler(int signal __attribute((unused))) {
  pthread_t self = pthread_self();
  int tnum = 0;
  while (tnum < 3) {
    if (tids[tnum] == self) {
      break;
    }
    tnum++;
  }

  fprintf(stderr, "Thread %i executes signal handler (%p)\n", tnum, self);
}

static void install_handler(void) {
  struct sigaction act;
  act.sa_handler = &sigusr1_handler;
  sigemptyset(&(act.sa_mask));
  act.sa_flags = 0;

  if (sigaction(SIGUSR1, &act, NULL) != 0) {
    fprintf(stderr, "Can't set signal handler: %s\n", strerror(errno));
    exit(1);
  }

  sigset_t sset;
  sigemptyset(&sset);
  sigaddset(&sset, SIGUSR1);
  if (sigprocmask(SIG_UNBLOCK, &sset, NULL) != 0) {
    fprintf(stderr, "Can't unblock SIGUSR1: %s\n", strerror(errno));
  }
}

int main() {
  fprintf(stderr, "Testing pthread_kill()\n\n");

  int i;
  int result;

  sem_init(&semaphore, 0, 0);
  install_handler();

  for (i=0; i<3; i++) {
    int *intptr = (int*)malloc(sizeof(int));
    *intptr = i;
    result = pthread_create(tids+i, NULL, &simplethread, intptr);
    if (result != 0) {
      fprintf(stderr, "Can't create thread: %s\n", strerror(result));
      return 1;
    }
  }

  sleep(1);
  install_handler();
  fprintf(stderr, "\n");

  int mainint = 42;
  pthread_cleanup_push(&cleanup_handler, &mainint);

  for (i=2; i>=0; i--) {
    fprintf(stderr, "Sending SIGUSR1 to thread %i (%p)\n", i, tids[i]);
    result = pthread_kill(tids[i], SIGUSR1);
    if (result != 0) {
      fprintf(stderr, "Error during pthread_kill: %s\n", strerror(result));
    }
    sleep(1);
  }

  pthread_cleanup_pop(0);
  return 0;
}