[checkmk-commits] Create a new process group and deliver signal to all processes in it.

Module: check_mk Branch: master Commit: c53e5502be58986e8a9599545c114242ec3a2a9f URL: http://git.mathias-kettner.de/git/?p=check_mk.git;a=commit;h=c53e5502be5898… Author: Sven Panne &lt;sp(a)mathias-kettner.de&gt; Date: Tue Nov 24 13:47:55 2015 +0100 Create a new process group and deliver signal to all processes in it. --- agents/waitmax.c | 42 ++++++++++++++++++++++++++++++++++++++---- 1 file changed, 38 insertions(+), 4 deletions(-) diff --git a/agents/waitmax.c b/agents/waitmax.c index c4205c8..3dab79d 100644 --- a/agents/waitmax.c +++ b/agents/waitmax.c @@ -87,9 +87,36 @@ static void usage(int status) 0, status); } -static void signalhandler(int signum __attribute__((__unused__))) +static void kill_group(pid_t pid, int signum) { - if (kill(g_pid, g_signum) == 0) g_timeout = 1; + /* The child might have become a process group leader itself, so send the + signal directly to it. */ + kill(pid, signum); + + /* Guard against harakiri... */ + signal(signum, SIG_IGN); + + /* Send the signal to all processes in our fresh process group. */ + kill(0, signum); +} + +static void signalhandler(int signum) +{ + if (signum == SIGALRM) { + /* The child took too long, so remember that we timed out and send the + configured signal instead of SIGALRM. */ + g_timeout = 1; + signum = g_signum; + } + + /* Are we the child process or has the child not been execvp'd yet? */ + if (g_pid == 0) exit(signum + 128); + + /* Send the configure signal to our process group. */ + kill_group(g_pid, signum); + + /* Make sure the children actually react on the signal. */ + if (signum != SIGKILL && signum != SIGCONT) kill_group(g_pid, SIGCONT); } static void setup_signal_handlers() @@ -110,8 +137,8 @@ static void setup_signal_handlers() sigaction(SIGTTIN, &sa, NULL); sigaction(SIGTTOU, &sa, NULL); - /* We do not want the parent's CHLD handling. */ - sa.sa_handler = SIG_IGN; + /* Make sure that waitpid won't fail. */ + sa.sa_handler = SIG_DFL; sigaction(SIGCHLD, &sa, NULL); } @@ -155,6 +182,13 @@ int main(int argc, char **argv) int maxtime = atoi(argv[optind]); if (maxtime <= 0) usage(1); + /* Create a new process group with ourselves as the process group + leader. This way we can send a signal to all subprocesses later (unless + some non-direct descendant creates its own process group). Doing this in + the parent process already simplifies things, because we don't have to + worry about foreground/background groups then. */ + setpgid(0, 0); + /* Setting up signal handlers before forking avoids race conditions with the child. */ setup_signal_handlers();