[checkmk-commits] Setup signal handlers in a way that we can forward signals for ourselves.

Module: check_mk Branch: master Commit: dfa3c0d685cdb308a92e797e0b7d260b21c55001 URL: http://git.mathias-kettner.de/git/?p=check_mk.git;a=commit;h=dfa3c0d685cdb3… Author: Sven Panne &lt;sp(a)mathias-kettner.de&gt; Date: Tue Nov 24 13:47:00 2015 +0100 Setup signal handlers in a way that we can forward signals for ourselves. --- agents/waitmax.c | 35 +++++++++++++++++++++++++++++++++-- 1 file changed, 33 insertions(+), 2 deletions(-) diff --git a/agents/waitmax.c b/agents/waitmax.c index 0a1cf4c..c4205c8 100644 --- a/agents/waitmax.c +++ b/agents/waitmax.c @@ -92,6 +92,29 @@ static void signalhandler(int signum __attribute__((__unused__))) if (kill(g_pid, g_signum) == 0) g_timeout = 1; } +static void setup_signal_handlers() +{ + struct sigaction sa; + sigemptyset(&sa.sa_mask); + sa.sa_handler = signalhandler; + sa.sa_flags = SA_RESTART; /* just to be sure... */ + sigaction(g_signum, &sa, NULL); + sigaction(SIGALRM, &sa, NULL); + sigaction(SIGHUP, &sa, NULL); + sigaction(SIGINT, &sa, NULL); + sigaction(SIGQUIT, &sa, NULL); + sigaction(SIGTERM, &sa, NULL); + + /* Guard against a background child doing I/O on the tty. */ + sa.sa_handler = SIG_IGN; + sigaction(SIGTTIN, &sa, NULL); + sigaction(SIGTTOU, &sa, NULL); + + /* We do not want the parent's CHLD handling. */ + sa.sa_handler = SIG_IGN; + sigaction(SIGCHLD, &sa, NULL); +} + static void unblock_signal(int signum) { sigset_t signals_to_unblock; @@ -132,18 +155,26 @@ int main(int argc, char **argv) int maxtime = atoi(argv[optind]); if (maxtime <= 0) usage(1); + /* Setting up signal handlers before forking avoids race conditions with the + child. */ + setup_signal_handlers(); + g_pid = fork(); if (g_pid == -1) exit_with("fork() failed", errno, 1); if (g_pid == 0) { - signal(SIGALRM, signalhandler); + /* Restore tty behavior in the child. */ + struct sigaction sa; + sa.sa_handler = SIG_DFL; + sigaction(SIGTTIN, &sa, NULL); + sigaction(SIGTTOU, &sa, NULL); + execvp(argv[optind + 1], argv + optind + 1); exit_with(argv[optind + 1], errno, 253); } /* Make sure SIGALRM is not blocked (e.g. by parent). */ unblock_signal(SIGALRM); - signal(SIGALRM, signalhandler); alarm(maxtime); int status;