#include <pthread.h>
#include <sched.h>
#include <setjmp.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
static pthread_attr_t attributes;
static int id[4] = {0, 1, 2, 3};
static pthread_t tid[4];
static bool state[4];
static bool blocking[4];
static pthread_key_t self;
static void
suspendLoop(int *i) {
sigjmp_buf env;
sigset_t mask;
sigsetjmp(env, false);
state[*i] = false;
sigfillset(&mask);
sigdelset(&mask, SIGUSR1);
sigdelset(&mask, SIGTERM);
while (state[*i] == false && blocking[*i] == false)
sigsuspend(&mask);
state[*i] = true;
}
static void
suspendHandler(int sig) {
int *i = (int*)pthread_getspecific(self);
suspendLoop(i);
}
static void
initialiseSignals()
{
struct sigaction act;
sigset_t mask;
act.sa_handler = suspendHandler;
sigemptyset(&act.sa_mask);
act.sa_flags = 0;
sigaction(SIGUSR1, &act, NULL);
sigemptyset(&mask);
sigaddset(&mask, SIGQUIT);
sigaddset(&mask, SIGINT);
sigaddset(&mask, SIGPIPE);
sigprocmask(SIG_BLOCK, &mask, NULL);
}
static void
self_suspend(int* i)
{
sigset_t mask;
blocking[*i] = false;
sigemptyset(&mask);
sigaddset(&mask, SIGUSR1);
pthread_sigmask(SIG_BLOCK, &mask, NULL);
printf("thread %d suspending\n", *i);
suspendLoop(i);
printf("thread %d suspend ended\n", *i);
pthread_sigmask(SIG_UNBLOCK, &mask, NULL);
}
void *
threadStart(void *arg)
{
int i = *(int*)arg;
pthread_setspecific(self, &i);
state[i] = true;
blocking[i] = true;
printf("threadStart(%d)\n", i);
for (int j = 0; j < 10; j++) {
usleep(1000000);
self_suspend(&i);
}
printf("quitting %d\n", i);
return NULL;
}
suspendAllThreads()
{
for (int i = 0; i < 4; i++) {
blocking[i] = false;
if (state[i] == true)
pthread_kill(tid[i], SIGUSR1);
}
for (int i = 0; i < 4; i++) {
while(state[i] == true) {
sched_yield();
}
}
}*/
void
resumeAllThreads()
{
for (int i = 0; i < 4; i++) {
blocking[i] = true;
if (state[i] == false) {
printf("thread %d signaled for resume\n", i);
pthread_kill(tid[i], SIGUSR1);
}
}
int t = 50;
for (int i = 0; i < 4; i++) {
while(state[i] == false && t-- > 0) {
printf("thread %d still suspended, yielding\n", i);
sched_yield();
}
}
}
int
main(int argc, char **argv)
{
initialiseSignals();
pthread_key_create(&self, NULL);
pthread_attr_init(&attributes);
pthread_attr_setdetachstate(&attributes, PTHREAD_CREATE_DETACHED);
for (int i = 0; i < 4; i++) {
if (pthread_create(&tid[i], &attributes, threadStart, &id[i]) != 0)
fprintf(stderr, "couldn't create thread %d\n", i);
printf("thread %d created\n", i);
}
printf("snoozing\n");
usleep(3000000);
printf("resuming all threads\n");
resumeAllThreads();
printf("resuming all threads done\n");
}
