Perform proper cleanup for signals with 'Term' action (#3057)

Issue #3049 describes a case where terminating i3 by means of SIGTERM
causes it to leak the runtime directory and all its contents. There are
multiple issues at play: first, any cleanup handlers registered via
atexit are never invoked when a signal terminates the program (see
atexit(3)). Hence, the log SHM log cleanup performed in i3_exit is not
invoked in that case. Second, compared to the shutdown path for the
'exit' command, we do not unlink the UNIX domain socket we create,
causing it to be leaked as well. Third, a handler for SIGTERM is not
registered at all despite handle_signal claiming to be the handler for
all 'Term' signals.
This change addresses all three problems and results in a graceful exit
including cleanup to happen when we receive a signal with the default
action 'Term'. It addresses issue #3049.

diff --git a/src/main.c b/src/main.c
index 98dba12c873537462765d1d181332d860f610945..b634b139f90276db0e4273d28a70922f732a63f5 100644 (file)
--- a/src/main.c
+++ b/src/main.c
@@ -174,21 +174,64 @@ static void i3_exit(void) {
         fflush(stderr);
         shm_unlink(shmlogname);
     }
+    ipc_shutdown(SHUTDOWN_REASON_EXIT);
+    unlink(config.ipc_socket_path);
 }
 
 /*
- * (One-shot) Handler for all signals with default action "Term", see signal(7)
+ * (One-shot) Handler for all signals with default action "Core", see signal(7)
  *
  * Unlinks the SHM log and re-raises the signal.
  *
  */
-static void handle_signal(int sig, siginfo_t *info, void *data) {
+static void handle_core_signal(int sig, siginfo_t *info, void *data) {
     if (*shmlogname != '\0') {
         shm_unlink(shmlogname);
     }
     raise(sig);
 }
 
+/*
+ * (One-shot) Handler for all signals with default action "Term", see signal(7)
+ *
+ * Exits the program gracefully.
+ *
+ */
+static void handle_term_signal(struct ev_loop *loop, ev_signal *signal, int revents) {
+    /* We exit gracefully here in the sense that cleanup handlers
+     * installed via atexit are invoked. */
+    exit(128 + signal->signum);
+}
+
+/*
+ * Set up handlers for all signals with default action "Term", see signal(7)
+ *
+ */
+static void setup_term_handlers(void) {
+    static struct ev_signal signal_watchers[6];
+    size_t num_watchers = sizeof(signal_watchers) / sizeof(signal_watchers[0]);
+
+    /* We have to rely on libev functionality here and should not use
+     * sigaction handlers because we need to invoke the exit handlers
+     * and cannot do so from an asynchronous signal handling context as
+     * not all code triggered during exit is signal safe (and exiting
+     * the main loop from said handler is not easily possible). libev's
+     * signal handlers does not impose such a constraint on us. */
+    ev_signal_init(&signal_watchers[0], handle_term_signal, SIGHUP);
+    ev_signal_init(&signal_watchers[1], handle_term_signal, SIGINT);
+    ev_signal_init(&signal_watchers[2], handle_term_signal, SIGALRM);
+    ev_signal_init(&signal_watchers[3], handle_term_signal, SIGTERM);
+    ev_signal_init(&signal_watchers[4], handle_term_signal, SIGUSR1);
+    ev_signal_init(&signal_watchers[5], handle_term_signal, SIGUSR1);
+    for (size_t i = 0; i < num_watchers; i++) {
+        ev_signal_start(main_loop, &signal_watchers[i]);
+        /* The signal handlers should not block ev_run from returning
+         * and so none of the signal handlers should hold a reference to
+         * the main loop. */
+        ev_unref(main_loop);
+    }
+}
+
 int main(int argc, char *argv[]) {
     /* Keep a symbol pointing to the I3_VERSION string constant so that we have
      * it in gdb backtraces. */
@@ -853,15 +896,15 @@ int main(int argc, char *argv[]) {
         err(EXIT_FAILURE, "pledge");
 #endif
 
-    struct sigaction action;
-
-    action.sa_sigaction = handle_signal;
-    action.sa_flags = SA_NODEFER | SA_RESETHAND | SA_SIGINFO;
-    sigemptyset(&action.sa_mask);
-
     if (!disable_signalhandler)
         setup_signal_handler();
     else {
+        struct sigaction action;
+
+        action.sa_sigaction = handle_core_signal;
+        action.sa_flags = SA_NODEFER | SA_RESETHAND | SA_SIGINFO;
+        sigemptyset(&action.sa_mask);
+
         /* Catch all signals with default action "Core", see signal(7) */
         if (sigaction(SIGQUIT, &action, NULL) == -1 ||
             sigaction(SIGILL, &action, NULL) == -1 ||
@@ -871,14 +914,7 @@ int main(int argc, char *argv[]) {
             ELOG("Could not setup signal handler.\n");
     }
 
-    /* Catch all signals with default action "Term", see signal(7) */
-    if (sigaction(SIGHUP, &action, NULL) == -1 ||
-        sigaction(SIGINT, &action, NULL) == -1 ||
-        sigaction(SIGALRM, &action, NULL) == -1 ||
-        sigaction(SIGUSR1, &action, NULL) == -1 ||
-        sigaction(SIGUSR2, &action, NULL) == -1)
-        ELOG("Could not setup signal handler.\n");
-
+    setup_term_handlers();
     /* Ignore SIGPIPE to survive errors when an IPC client disconnects
      * while we are sending them a message */
     signal(SIGPIPE, SIG_IGN);

diff --git a/testcases/lib/i3test.pm.in b/testcases/lib/i3test.pm.in
index ed239241c84dadba0412c3609701d6cf957c5505..e754c0c17f6bf3b8b5b92e72233ebbe05ab8198a 100644 (file)
--- a/testcases/lib/i3test.pm.in
+++ b/testcases/lib/i3test.pm.in
@@ -12,6 +12,7 @@ use AnyEvent::I3;
 use List::Util qw(first);
 use Time::HiRes qw(sleep);
 use Cwd qw(abs_path);
+use POSIX ':sys_wait_h';
 use Scalar::Util qw(blessed);
 use SocketActivation;
 use i3test::Util qw(slurp);
@@ -37,6 +38,7 @@ our @EXPORT = qw(
     cmd
     sync_with_i3
     exit_gracefully
+    exit_forcefully
     workspace_exists
     focused_ws
     get_socket_path
@@ -123,7 +125,7 @@ END {
 
     } else {
         kill(-9, $i3_pid)
-            or $tester->BAIL_OUT("could not kill i3");
+            or $tester->BAIL_OUT("could not kill i3: $!");
 
         waitpid $i3_pid, 0;
     }
@@ -759,7 +761,7 @@ sub exit_gracefully {
 
     if (!$exited) {
         kill(9, $pid)
-            or $tester->BAIL_OUT("could not kill i3");
+            or $tester->BAIL_OUT("could not kill i3: $!");
     }
 
     if ($socketpath =~ m,^/tmp/i3-test-socket-,) {
@@ -770,6 +772,47 @@ sub exit_gracefully {
     undef $i3_pid;
 }
 
+=head2 exit_forcefully($pid, [ $signal ])
+
+Tries to exit i3 forcefully by sending a signal (defaults to SIGTERM).
+
+You only need to use this function if you want to test signal handling
+(in which case you must have launched i3 on your own with
+C<launch_with_config>).
+
+  use i3test i3_autostart => 0;
+  my $pid = launch_with_config($config);
+  # …
+  exit_forcefully($pid);
+
+=cut
+sub exit_forcefully {
+    my ($pid, $signal) = @_;
+    $signal ||= 'TERM';
+
+    # Send the given signal to the i3 instance and wait for up to 10s
+    # for it to terminate.
+    kill($signal, $pid)
+        or $tester->BAIL_OUT("could not kill i3: $!");
+    my $status;
+    my $timeout = 10;
+    do {
+        $status = waitpid $pid, WNOHANG;
+
+        if ($status <= 0) {
+            sleep(1);
+            $timeout--;
+        }
+    } while ($status <= 0 && $timeout > 0);
+
+    if ($status <= 0) {
+        kill('KILL', $pid)
+            or $tester->BAIL_OUT("could not kill i3: $!");
+        waitpid $pid, 0;
+    }
+    undef $i3_pid;
+}
+
 =head2 get_socket_path([ $cache ])
 
 Gets the socket path from the C<I3_SOCKET_PATH> atom stored on the X11 root

diff --git a/testcases/t/540-sigterm-cleanup.t b/testcases/t/540-sigterm-cleanup.t
new file mode 100644 (file)
index 0000000..5e5b9bf
--- /dev/null
+++ b/testcases/t/540-sigterm-cleanup.t
@@ -0,0 +1,35 @@
+#!perl
+# vim:ts=4:sw=4:expandtab
+#
+# Please read the following documents before working on tests:
+# • https://build.i3wm.org/docs/testsuite.html
+#   (or docs/testsuite)
+#
+# • https://build.i3wm.org/docs/lib-i3test.html
+#   (alternatively: perldoc ./testcases/lib/i3test.pm)
+#
+# • https://build.i3wm.org/docs/ipc.html
+#   (or docs/ipc)
+#
+# • http://onyxneon.com/books/modern_perl/modern_perl_a4.pdf
+#   (unless you are already familiar with Perl)
+#
+# Tests that the socket file is cleaned up properly after gracefully
+# shutting down i3 via SIGTERM.
+# Ticket: #3049
+use i3test i3_autostart => 0;
+
+my $config = <<EOT;
+# i3 config file (v4)
+font -misc-fixed-medium-r-normal--13-120-75-75-C-70-iso10646-1
+EOT
+
+my $pid = launch_with_config($config, dont_add_socket_path => 1);
+my $socket = get_socket_path();
+ok(-S $socket, "socket $socket exists");
+
+exit_forcefully($pid, 'TERM');
+
+ok(!-e $socket, "socket $socket no longer exists");
+
+done_testing;