4774179cb
Denis Vlasenko
2009-03-10
Subject
mail.c: more robust handling of SIGCHLD init: more robust signal handling
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init/init.c+23 -18
| @@ -336,20 +336,22 @@ static pid_t run(const struct init_action *a) | |
| { | |
| pid_t pid; | |
| + | /* Careful: don't be affected by a signal in vforked child */ |
| + | sigprocmask_allsigs(SIG_BLOCK); |
| if (BB_MMU && (a->action_type & ASKFIRST)) | |
| pid = fork(); | |
| else | |
| pid = vfork(); | |
| if (pid < 0) | |
| message(L_LOG | L_CONSOLE, "can't fork"); | |
| - | if (pid) |
| + | if (pid) { |
| + | sigprocmask_allsigs(SIG_UNBLOCK); |
| return pid; /* Parent or error */ | |
| + | } |
| /* Child */ | |
| /* Reset signal handlers that were set by the parent process */ | |
| - | //TODO: block signals across fork(), prevent them to affect child before |
| - | //signals are reset? |
| bb_signals(0 | |
| + (1 << SIGUSR1) | |
| + (1 << SIGUSR2) | |
| @@ -359,6 +361,7 @@ static pid_t run(const struct init_action *a) | |
| + (1 << SIGHUP) | |
| + (1 << SIGTSTP) | |
| , SIG_DFL); | |
| + | sigprocmask_allsigs(SIG_UNBLOCK); |
| /* Create a new session and make ourself the process group leader */ | |
| setsid(); | |
| @@ -982,40 +985,42 @@ int init_main(int argc UNUSED_PARAM, char **argv) | |
| * NB: if delayed signal happened, avoid blocking in wait(). | |
| */ | |
| while (1) { | |
| - | pid_t wpid; |
| - | int got_sigs; |
| + | int maybe_WNOHANG; |
| - | got_sigs = check_delayed_sigs(); |
| + | maybe_WNOHANG = check_delayed_sigs(); |
| /* (Re)run the respawn/askfirst stuff */ | |
| run_actions(RESPAWN | ASKFIRST); | |
| - | |
| - | got_sigs |= check_delayed_sigs(); |
| + | maybe_WNOHANG |= check_delayed_sigs(); |
| /* Don't consume all CPU time - sleep a bit */ | |
| sleep(1); | |
| + | maybe_WNOHANG |= check_delayed_sigs(); |
| - | got_sigs |= check_delayed_sigs(); |
| - | |
| - | if (got_sigs) |
| - | goto dont_block; |
| - | /* Wait for any child process to exit. |
| + | /* Wait for any child process(es) to exit. |
| * NB: "delayed" signals will also interrupt this wait(), | |
| * bb_signals_recursive_norestart() set them up for that. | |
| * This guarantees we won't be stuck here | |
| * till next orphan dies. | |
| */ | |
| - | wpid = wait(NULL); |
| - | while (wpid > 0) { |
| - | struct init_action *a = mark_terminated(wpid); |
| + | if (maybe_WNOHANG) |
| + | maybe_WNOHANG = WNOHANG; |
| + | while (1) { |
| + | pid_t wpid; |
| + | struct init_action *a; |
| + | |
| + | wpid = waitpid(-1, NULL, maybe_WNOHANG); |
| + | if (wpid <= 0) |
| + | break; |
| + | |
| + | a = mark_terminated(wpid); |
| if (a) { | |
| message(L_LOG, "process '%s' (pid %d) exited. " | |
| "Scheduling for restart.", | |
| a->command, wpid); | |
| } | |
| /* See if anyone else is waiting to be reaped */ | |
| - | dont_block: |
| - | wpid = wait_any_nohang(NULL); |
| + | maybe_WNOHANG = WNOHANG; |
| } | |
| } /* while (1) */ | |
| } | |
mailutils/mail.c+7 -4
| @@ -48,6 +48,12 @@ void FAST_FUNC launch_helper(const char **argv) | |
| xpipe(pipes); | |
| xpipe(pipes + 2); | |
| + | // NB: handler must be installed before vfork |
| + | bb_signals(0 |
| + | + (1 << SIGCHLD) |
| + | + (1 << SIGALRM) |
| + | , signal_handler); |
| + | |
| G.helper_pid = vfork(); | |
| if (G.helper_pid < 0) | |
| bb_perror_msg_and_die("vfork"); | |
| @@ -60,15 +66,12 @@ void FAST_FUNC launch_helper(const char **argv) | |
| if (!G.helper_pid) { | |
| // child: try to execute connection helper | |
| + | // NB: SIGCHLD & SIGALRM revert to SIG_DFL on exec |
| BB_EXECVP(*argv, (char **)argv); | |
| _exit(127); | |
| } | |
| // parent | |
| - | bb_signals(0 |
| - | + (1 << SIGCHLD) |
| - | + (1 << SIGALRM) |
| - | , signal_handler); |
| // check whether child is alive | |
| //redundant:signal_handler(SIGCHLD); | |
| // child seems OK -> parent goes on | |