Greetings all,
I have this server (running on Linux 2.6.17-gentoo-r9) that I've been tinkering with and I attempted to do a multi-threaded model to accept multiple connections, however I found that it was leaving zombie processes and not cleaning up after itself at all. The main thread was doing a waitpid((pid_t)-1, Null, WNOHANG) and keeping track of the number of clients it created/cleaned up. Since that did not work as I had expected I decided to try and allow only a single connection (ie, wait(NULL) causing the main thread to not listen for client connections until it cleaned up its child). While this works great and appears to clean up children when monitoring ps, when I watch 'top' it seems that used memory just constantly increases once the first client thread is spawned. After it is closed the used memory goes down a little, but then ever-so-slowly increases. If I remove the client threading all together the used memory does not fluctuate. Could somebody please peruse this threading model code I have posted below and tell me if I'm doing something blatently dumb?! I would greatly appreciate it! - int main(char argc, char *argv[])
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{
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pid_t pid;
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pid_t process_id;
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struct sigaction sa;
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int error;
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int sockfd;
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int ss_fd;
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char response[MAX_MSG_BUFF_SIZE];
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-
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sprintf(VersionString, "Daemon v %d.%d.%d", MajorVersion,
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MinorVersion, PatchVersion);
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/* Spawn the daemon */
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pid = fork();
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if (pid < 0) {
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printf("Failed PID #0\n");
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exit(EXIT_FAILURE);
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}
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else if (pid > 0) {
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exit(EXIT_SUCCESS);
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}
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sid = setsid();
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if (sid < 0) {
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printf("Failed SID\n");
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exit(EXIT_FAILURE);
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}
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/* Set up and install handler for signal SIGTERM */
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memset(&sa, 0, sizeof(sa));
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sa.sa_handler = &sigterm_handler;
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sigemptyset(&sa.sa_mask);
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sa.sa_flags = 0;
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sigaction(SIGTERM, &sa, NULL);
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/* Set up and install handler for signal SIGINT */
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memset(&sa, 0, sizeof(sa));
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sa.sa_handler = &sigint_handler;
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sigemptyset(&sa.sa_mask);
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sa.sa_flags = 0;
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sigaction(SIGINT, &sa, NULL);
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ss_fd = ds_open_server(DSTREAM_PORT);
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if (ss_fd == -1) {
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printf("ds_open_server socket error\n");
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exit(1);
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}
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while (!quit_daemon)
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{
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sockfd = 0;
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if ((sockfd = ds_listen_for_client(ss_fd, BACKLOG)) > 0)
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{
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if (client_cnt > 5)
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{
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strcpy(response, "MAX_CLIENTS");
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ds_send(sockfd, response, strlen(response));
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ds_close(sockfd);
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sleep(SLEEP_TIME);
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}
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else
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{
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pid = fork();
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if (pid > 0)
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{
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client_cnt++;
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while (client_cnt)
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{
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process_id = wait(NULL);
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/* This was causing zombie processes */
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//process_id = waitpid((pid_t) -1, NULL, WNOHANG); /* non-blocking wait */
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if (process_id < 0)
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{ /* waitpid error */
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perror("waitpid");
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}
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else if (process_id == 0)
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{ /* no zombies to wait on */
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break;
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}
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else
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{
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client_cnt--;
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//printf("Stopped child process %d\n", process_id);
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}
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}
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}
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else
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{
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if ((error = StartDataStreamer(sockfd)))
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{
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printf("Exiting with error = %d\n", error);
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StopDataStreamer();
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exit(EXIT_FAILURE);
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}
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else
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{
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// printf("Datastreamer started successfully: %d\n", sockfd);
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while (!quit_client)
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{
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// printf("sleeping client %d\n",sockfd);
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sleep(SLEEP_TIME);
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}
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exit(EXIT_SUCCESS);
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} // end else
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} // end else
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} // end else
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} // end if
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} // end while
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ds_close_server(ss_fd);
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exit(EXIT_SUCCESS);
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} // end main
And by the way, the ds_* functions are just wrappers I made to simplify the amount of typing for sending/receiving/opening connections etc. And then StartDataStreamer is the actual code that does the work of transferring data back and forth from my other computer. StopDataStreamer just shuts everything down (raising quit_daemon). I don't see why this would cause a memory leak, and also if anybody has any idea why the original waitpid method was leaving zombies I'd love to hear your thoughts.
Thanks in advance!
James
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