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core: improve handling of POSIX signals using sigwait() (rh #739836)
There are multiple ways how to handle standard unix signals. They work quite well for a single-threaded application. However, signal handling in a multi- threaded app becomes tricky. And, the most safe way is to use sigwait() function in a dedicated thread, which allows us to process the signals synchronously and thus avoid various nasty problems. A few useful links: http://pubs.opengroup.org/onlinepubs/007904975/functions/sigwait.html http://pic.dhe.ibm.com/infocenter/aix/v6r1/index.jsp?topic=%2Fcom.ibm.aix.genprogc%2Fdoc%2Fgenprogc%2Fsignal_mgmt.htm http://www.linuxjournal.com/article/2121?page=0,2 http://www.redwoodsoft.com/~dru/unixbook/book.chinaunix.net/special/ebook/addisonWesley/APUE2/0201433079/ch12lev1sec8.html
This commit is contained in:
Jiří Klimeš
parent
21bc3ab517
commit
217c5bf6ac
1 changed files with 89 additions and 83 deletions
172
src/main.c
172
src/main.c
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@ -29,6 +29,7 @@
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#include <errno.h>
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#include <stdlib.h>
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#include <signal.h>
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#include <pthread.h>
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#include <unistd.h>
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#include <fcntl.h>
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#include <sys/stat.h>
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@ -66,101 +67,104 @@
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*/
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static NMManager *manager = NULL;
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static GMainLoop *main_loop = NULL;
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static int quit_pipe[2] = { -1, -1 };
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static gboolean quit_early = FALSE;
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static sigset_t signal_set;
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static void
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nm_signal_handler (int signo)
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void *signal_handling_thread (void *arg);
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/*
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* Thread function waiting for signals and processing them.
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* Wait for signals in signal set. The semantics of sigwait() require that all
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* threads (including the thread calling sigwait()) have the signal masked, for
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* reliable operation. Otherwise, a signal that arrives while this thread is
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* not blocked in sigwait() might be delivered to another thread.
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*/
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void *
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signal_handling_thread (void *arg)
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{
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static int in_fatal = 0, x;
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int signo;
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/* avoid loops */
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if (in_fatal > 0)
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return;
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++in_fatal;
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while (1) {
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sigwait (&signal_set, &signo);
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switch (signo) {
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case SIGSEGV:
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case SIGBUS:
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case SIGILL:
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case SIGABRT:
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nm_log_warn (LOGD_CORE, "caught signal %d. Generating backtrace...", signo);
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nm_logging_backtrace ();
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exit (1);
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break;
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case SIGFPE:
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case SIGPIPE:
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/* let the fatal signals interrupt us */
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--in_fatal;
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nm_log_warn (LOGD_CORE, "caught signal %d, shutting down abnormally. Generating backtrace...", signo);
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nm_logging_backtrace ();
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x = write (quit_pipe[1], "X", 1);
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break;
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case SIGINT:
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case SIGTERM:
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/* let the fatal signals interrupt us */
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--in_fatal;
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nm_log_info (LOGD_CORE, "caught signal %d, shutting down normally.", signo);
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quit_early = TRUE;
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x = write (quit_pipe[1], "X", 1);
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break;
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case SIGHUP:
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--in_fatal;
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/* Reread config stuff like system config files, VPN service files, etc */
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break;
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case SIGUSR1:
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--in_fatal;
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/* Play with log levels or something */
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break;
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default:
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signal (signo, nm_signal_handler);
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break;
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}
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switch (signo) {
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case SIGSEGV:
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case SIGBUS:
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case SIGILL:
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case SIGABRT:
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case SIGQUIT:
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nm_log_warn (LOGD_CORE, "caught signal %d. Generating backtrace...", signo);
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nm_logging_backtrace ();
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exit (1);
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break;
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case SIGFPE:
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case SIGPIPE:
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nm_log_warn (LOGD_CORE, "caught signal %d, shutting down abnormally. Generating backtrace...", signo);
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nm_logging_backtrace ();
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quit_early = TRUE; /* for quitting before entering the main loop */
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g_main_loop_quit (main_loop);
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break;
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case SIGINT:
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case SIGTERM:
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nm_log_info (LOGD_CORE, "caught signal %d, shutting down normally.", signo);
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quit_early = TRUE; /* for quitting before entering the main loop */
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g_main_loop_quit (main_loop);
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break;
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case SIGHUP:
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/* Reread config stuff like system config files, VPN service files, etc */
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nm_log_info (LOGD_CORE, "caught signal %d, not supported yet.", signo);
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break;
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case SIGUSR1:
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/* Play with log levels or something */
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nm_log_info (LOGD_CORE, "caught signal %d, not supported yet.", signo);
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break;
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default:
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nm_log_err (LOGD_CORE, "caught unexpected signal %d", signo);
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break;
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}
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}
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return NULL;
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}
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/*
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* Mask the signals we are interested in and create a signal handling thread.
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* Because all threads inherit the signal mask from their creator, all threads
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* in the process will have the signals masked. That's why setup_signals() has
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* to be called before creating other threads.
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*/
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static gboolean
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quit_watch (GIOChannel *src, GIOCondition condition, gpointer user_data)
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{
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if (condition & G_IO_IN) {
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nm_log_warn (LOGD_CORE, "quit request received, terminating...");
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g_main_loop_quit (main_loop);
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}
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return FALSE;
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}
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static void
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setup_signals (void)
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{
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struct sigaction action;
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sigset_t mask;
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GIOChannel *quit_channel;
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pthread_t signal_thread_id;
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int status;
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/* Set up our quit pipe */
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if (pipe (quit_pipe) < 0) {
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fprintf (stderr, _("Failed to initialize SIGTERM pipe: %d"), errno);
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exit (1);
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sigemptyset (&signal_set);
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sigaddset (&signal_set, SIGHUP);
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sigaddset (&signal_set, SIGINT);
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sigaddset (&signal_set, SIGQUIT);
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sigaddset (&signal_set, SIGILL);
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sigaddset (&signal_set, SIGABRT);
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sigaddset (&signal_set, SIGFPE);
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sigaddset (&signal_set, SIGBUS);
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sigaddset (&signal_set, SIGSEGV);
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sigaddset (&signal_set, SIGPIPE);
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sigaddset (&signal_set, SIGTERM);
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sigaddset (&signal_set, SIGUSR1);
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/* Block all signals of interest. */
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status = pthread_sigmask (SIG_BLOCK, &signal_set, NULL);
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if (status != 0) {
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fprintf (stderr, _("Failed to set signal mask: %d"), status);
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return FALSE;
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}
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fcntl (quit_pipe[1], F_SETFL, O_NONBLOCK | fcntl (quit_pipe[1], F_GETFL));
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quit_channel = g_io_channel_unix_new (quit_pipe[0]);
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g_io_add_watch_full (quit_channel, G_PRIORITY_HIGH, G_IO_IN | G_IO_ERR, quit_watch, NULL, NULL);
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/* Create the signal handling thread. */
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status = pthread_create (&signal_thread_id, NULL, signal_handling_thread, NULL);
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if (status != 0) {
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fprintf (stderr, _("Failed to create signal handling thread: %d"), status);
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return FALSE;
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}
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sigemptyset (&mask);
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action.sa_handler = nm_signal_handler;
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action.sa_mask = mask;
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action.sa_flags = 0;
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sigaction (SIGTERM, &action, NULL);
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sigaction (SIGINT, &action, NULL);
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sigaction (SIGILL, &action, NULL);
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sigaction (SIGBUS, &action, NULL);
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sigaction (SIGFPE, &action, NULL);
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sigaction (SIGHUP, &action, NULL);
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sigaction (SIGSEGV, &action, NULL);
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sigaction (SIGABRT, &action, NULL);
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sigaction (SIGUSR1, &action, NULL);
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return TRUE;
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}
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static gboolean
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@ -393,6 +397,10 @@ main (int argc, char *argv[])
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exit (1);
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}
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/* Set up unix signal handling */
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if (!setup_signals ())
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exit (1);
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/* Set locale to be able to use environment variables */
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setlocale (LC_ALL, "");
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@ -529,8 +537,6 @@ main (int argc, char *argv[])
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dbus_glib_global_set_disable_legacy_property_access ();
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#endif
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setup_signals ();
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nm_logging_start (become_daemon);
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nm_log_info (LOGD_CORE, "NetworkManager (version " NM_DIST_VERSION ") is starting...");
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