Race condition

blog/way_too_many_ways_to_wait_for_a_child_process_with_a_timeout.html

Lines 336 to 360 in ebb19f4

    
6273
 
           int child_pid = fork(); 
        
           if (-1 == child_pid) { 
        
             return errno; 
        
           } 
        
           if (0 == child_pid) { // Child 
        
             argv += 1; 
        
             if (-1 == execvp(argv[0], argv)) { 
        
               return errno; 
        
             } 
        
             __builtin_unreachable(); 
        
           } 
        
           sigset_t sigset = {0}; 
        
           sigemptyset(&amp;sigset); 
        
           sigaddset(&amp;sigset, SIGCHLD); 
        
           siginfo_t siginfo = {0}; 
        
           struct timespec timeout = { 
        
               .tv_sec = wait_ms / 1000, 
        
               .tv_nsec = (wait_ms % 1000) * 1000 * 1000, 
        
           }; 
        
           int sig = sigtimedwait(&amp;sigset, &amp;siginfo, &amp;timeout);

SIGCHLD may come after fork() and before sigtimedwait().

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	int child_pid = fork();
	if (-1 == child_pid) {
	return errno;
	}

	if (0 == child_pid) { // Child
	argv += 1;
	if (-1 == execvp(argv[0], argv)) {
	return errno;
	}
	__builtin_unreachable();
	}

	sigset_t sigset = {0};
	sigemptyset(&sigset);
	sigaddset(&sigset, SIGCHLD);

	siginfo_t siginfo = {0};

	struct timespec timeout = {
	.tv_sec = wait_ms / 1000,
	.tv_nsec = (wait_ms % 1000) * 1000 * 1000,
	};

	int sig = sigtimedwait(&sigset, &siginfo, &timeout);

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