Simplify dumb-init behavior using sigwait
This commit is contained in:
Chris Kuehl
parent
6faf204a0b
commit
256edaef74
2 changed files with 45 additions and 54 deletions
97
dumb-init.c
97
dumb-init.c
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@ -35,12 +35,8 @@ char debug = 0;
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char use_setsid = 1;
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void forward_signal(int signum) {
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if (child_pid > 0) {
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kill(use_setsid ? -child_pid : child_pid, signum);
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DEBUG("Forwarded signal %d to children.\n", signum);
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} else {
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DEBUG("Didn't forward signal %d, no children exist yet.\n", signum);
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}
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kill(use_setsid ? -child_pid : child_pid, signum);
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DEBUG("Forwarded signal %d to children.\n", signum);
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}
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/*
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@ -78,8 +74,26 @@ void forward_signal(int signum) {
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*/
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void handle_signal(int signum) {
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DEBUG("Received signal %d.\n", signum);
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if (signum == SIGCHLD) {
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int status, exit_status;
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pid_t killed_pid;
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while ((killed_pid = waitpid(-1, &status, WNOHANG)) > 0) {
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if (WIFEXITED(status)) {
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exit_status = WEXITSTATUS(status);
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DEBUG("A child with PID %d exited with exit status %d.\n", killed_pid, exit_status);
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} else {
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assert(WIFSIGNALED(status));
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exit_status = 128 + WTERMSIG(status);
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DEBUG("A child with PID %d was terminated by signal %d.\n", killed_pid, exit_status - 128);
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}
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if (
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if (killed_pid == child_pid) {
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forward_signal(SIGTERM); // send SIGTERM to any remaining children
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DEBUG("Child exited with status %d. Goodbye.\n", exit_status);
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exit(exit_status);
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}
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}
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} else if (
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signum == SIGTSTP || // tty: background yourself
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signum == SIGTTIN || // tty: stop reading
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signum == SIGTTOU // tty: stop writing
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@ -121,9 +135,9 @@ void print_help(char *argv[]) {
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);
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}
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int main(int argc, char *argv[]) {
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int signum, opt;
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char **parse_command(int argc, char *argv[]) {
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int opt;
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struct option long_options[] = {
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{"help", no_argument, NULL, 'h'},
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{"single-child", no_argument, NULL, 'c'},
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@ -134,18 +148,18 @@ int main(int argc, char *argv[]) {
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switch (opt) {
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case 'h':
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print_help(argv);
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return 0;
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exit(0);
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case 'v':
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debug = 1;
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break;
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case 'V':
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fprintf(stderr, "dumb-init v%s", VERSION);
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return 0;
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exit(0);
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case 'c':
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use_setsid = 0;
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break;
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default:
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return 1;
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exit(1);
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}
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}
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@ -156,9 +170,8 @@ int main(int argc, char *argv[]) {
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"Try %s --help for full usage.\n",
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argv[0], argv[0]
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);
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return 1;
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exit(1);
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}
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char **cmd = &argv[optind];
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char *debug_env = getenv("DUMB_INIT_DEBUG");
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if (debug_env && strcmp(debug_env, "1") == 0) {
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@ -172,29 +185,20 @@ int main(int argc, char *argv[]) {
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DEBUG("Not running in setsid mode.\n");
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}
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/* register signal handlers */
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for (signum = 1; signum < 32; signum++) {
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if (signum == SIGKILL || signum == SIGSTOP || signum == SIGCHLD)
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continue;
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return &argv[optind];
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}
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if (signal(signum, handle_signal) == SIG_ERR) {
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PRINTERR("Couldn't register signal handler for signal `%d`. Exiting.\n", signum);
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return 1;
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}
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}
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int main(int argc, char *argv[]) {
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char **cmd = parse_command(argc, argv);
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/* launch our process */
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child_pid = fork();
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if (child_pid < 0) {
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PRINTERR("Unable to fork. Exiting.\n");
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return 1;
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}
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if (child_pid == 0) {
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} else if (child_pid == 0) {
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/* child */
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if (use_setsid) {
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pid_t result = setsid();
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if (result == -1) {
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if (setsid() == -1) {
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PRINTERR(
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"Unable to setsid (errno=%d %s). Exiting.\n",
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errno,
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@ -204,37 +208,22 @@ int main(int argc, char *argv[]) {
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}
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DEBUG("setsid complete.\n");
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}
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execvp(cmd[0], &cmd[0]);
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// if this point is reached, exec failed, so we should exit nonzero
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PRINTERR("%s: %s\n", argv[1], strerror(errno));
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exit(2);
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return 2;
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} else {
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pid_t killed_pid;
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int exit_status, status;
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/* parent */
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int signum;
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sigset_t all_signals;
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sigfillset(&all_signals);
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sigprocmask(SIG_BLOCK, &all_signals, NULL);
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DEBUG("Child spawned with PID %d.\n", child_pid);
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while ((killed_pid = waitpid(-1, &status, 0))) {
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if (WIFEXITED(status)) {
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exit_status = WEXITSTATUS(status);
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DEBUG("A child with PID %d exited with exit status %d.\n", killed_pid, exit_status);
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} else {
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assert(WIFSIGNALED(status));
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exit_status = 128 + WTERMSIG(status);
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DEBUG("A child with PID %d was terminated by signal %d.\n", killed_pid, exit_status - 128);
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}
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if (killed_pid == child_pid) {
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// send SIGTERM to any remaining children
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forward_signal(SIGTERM);
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DEBUG("Child exited with status %d. Goodbye.\n", exit_status);
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exit(exit_status);
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}
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for (;;) {
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sigwait(&all_signals, &signum);
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handle_signal(signum);
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}
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}
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return 0;
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}
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@ -69,6 +69,7 @@ def test_verbose(flag):
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(
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b'^\[dumb-init\] Child spawned with PID [0-9]+\.\n'
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b'\[dumb-init\] setsid complete\.\n'
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b'\[dumb-init\] Received signal 17\.\n'
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b'\[dumb-init\] A child with PID [0-9]+ exited with exit status 0.\n'
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b'\[dumb-init\] Forwarded signal 15 to children\.\n'
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b'\[dumb-init\] Child exited with status 0\. Goodbye\.\n$'
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@ -88,6 +89,7 @@ def test_verbose_and_single_child(flag1, flag2):
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assert re.match(
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(
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b'^\[dumb-init\] Child spawned with PID [0-9]+\.\n'
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b'\[dumb-init\] Received signal 17\.\n'
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b'\[dumb-init\] A child with PID [0-9]+ exited with exit status 0.\n'
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b'\[dumb-init\] Forwarded signal 15 to children\.\n'
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b'\[dumb-init\] Child exited with status 0\. Goodbye\.\n$'
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