Fix signal handling and work around a udev bug

Switch to ppoll() to avoid a race condition while handling signals
(see the ppoll/pselect manpages) and also work around the udev bug
that causes child processes to inherit udev's signal mask (which
masks everything).

1 files changed, 20 insertions, 4 deletions

diff --git a/daemon/main.c b/daemon/main.c
index 7c38166..0557f0e 100644
--- a/daemon/main.c
+++ b/daemon/main.c
@@ -21,6 +21,7 @@ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 */
 
 #define _BSD_SOURCE
+#define _GNU_SOURCE
 
 #ifdef HAVE_CONFIG_H
 #include <config.h>
@@ -126,6 +127,17 @@ void handle_signal(int sig)
 void set_signal_handlers(void)
 {
         struct sigaction sa;
+        sigset_t set;
+
+        // Mask all signals we handle. They will be unmasked by ppoll().
+        sigemptyset(&set);
+        sigaddset(&set, SIGINT);
+        sigaddset(&set, SIGQUIT);
+        sigaddset(&set, SIGTERM);
+        sigaddset(&set, SIGUSR1);
+        sigaddset(&set, SIGUSR2);
+        sigprocmask(SIG_SETMASK, &set, NULL);
+        
         memset(&sa, 0, sizeof(struct sigaction));
         sa.sa_handler = handle_signal;
         sigaction(SIGINT, &sa, NULL);
@@ -139,6 +151,10 @@ int main_loop(int listenfd)
 {
         int to, cnt, i, dto;
         struct fdlist pollfds;
+        struct timespec tspec;
+
+        sigset_t empty_sigset;
+        sigemptyset(&empty_sigset); // unmask all signals
 
         fdlist_create(&pollfds);
         while(!should_exit) {
@@ -156,15 +172,15 @@ int main_loop(int listenfd)
                 client_get_fds(&pollfds);
                 usbmuxd_log(LL_FLOOD, "fd count is %d", pollfds.count);
 
-                cnt = poll(pollfds.fds, pollfds.count, to);
+                tspec.tv_sec = to / 1000;
+                tspec.tv_nsec = (to % 1000) * 1000000;
+                cnt = ppoll(pollfds.fds, pollfds.count, &tspec, &empty_sigset);
                 usbmuxd_log(LL_FLOOD, "poll() returned %d", cnt);
-
                 if(cnt == -1) {
                         if(errno == EINTR) {
                                 if(should_exit) {
                                         usbmuxd_log(LL_INFO, "Event processing interrupted");
-                                        fdlist_free(&pollfds);
-                                        return 0;
+                                        break;
                                 }
                                 if(should_discover) {
                                         should_discover = 0;