Fix handling of SIGCHLD

The commit that removed metacity-dialog added a global SIGCHLD handler
that caused problems by (a) calling waitpid(-1) and thus breaking
g_child_watch for everyone else, and (b) doing too much from a signal
handler and sometimes causing deadlocks (bug 596200).

This removes the global handler and has each zenity user create its
own child watch to watch for exit. (It also fixes the window class of
the zenity dialogs, so that meta_window_present_delete_dialog() will
work again.)

src/core/delete.c

@@ -55,27 +55,16 @@ delete_ping_reply_func (MetaDisplay *display,
   /* we do nothing */
 }
 
-static gboolean
-delete_window_callback (gpointer w_p)
-{
-  meta_window_kill ((MetaWindow*) w_p);
-
-  return FALSE; /* don't do it again */
-}
-
 static void
-sigchld_handler (MetaNexus *nexus, guint arg1, gpointer arg2, gpointer user_data)
+dialog_exited (GPid pid, int status, gpointer user_data)
 {
   MetaWindow *ours = (MetaWindow*) user_data;
 
-  if (GPOINTER_TO_INT (arg2) == ours->dialog_pid)
+  ours->dialog_pid = -1;
-    {
-      if (arg1 == 1 /* pressed "force quit" */)
-        g_idle_add_full (G_PRIORITY_DEFAULT,
-                         delete_window_callback, user_data, NULL);
 
-      ours->dialog_pid = -1; /* forget it anyway */
+  /* exit status of 1 means the user pressed "Force Quit" */
-    }
+  if (WIFEXITED (status) && WEXITSTATUS (status) == 1)
+    meta_window_kill (ours);
 }
 
 static void
@@ -119,11 +108,7 @@ delete_ping_timeout_func (MetaDisplay *display,
   g_free (window_content);
 
   window->dialog_pid = dialog_pid;
-
+  g_child_watch_add (dialog_pid, dialog_exited, window);
-  g_signal_connect (sigchld_nexus, "sigchld",
-                    G_CALLBACK (sigchld_handler),
-                    window);
-
 }
 
 void

src/core/main.c

@@ -444,29 +444,6 @@ sigterm_handler (int signum)
   exit (meta_exit_code);
 }
 
-static guint sigchld_signal_id = 0;
-
-static void
-sigchld_handler (int signum, siginfo_t *info, void *context)
-{
-  int stat;
-
-  if (info->si_code == CLD_EXITED)
-    {
-      g_signal_emit (sigchld_nexus, sigchld_signal_id, 0,
-                     info->si_status,
-                     GINT_TO_POINTER (info->si_pid));
-    }
-
-  g_signal_handlers_disconnect_matched (sigchld_nexus,
-                                        G_SIGNAL_MATCH_DATA,
-                                        sigchld_signal_id,
-                                        0, NULL, NULL,
-                                        GINT_TO_POINTER (info->si_pid));
-
-  waitpid (info->si_pid, &stat, WNOHANG);
-}
-    
 /**
  * This is where the story begins. It parses commandline options and
  * environment variables, sets up the screen, hands control off to
@@ -517,24 +494,6 @@ main (int argc, char **argv)
     g_printerr ("Failed to register SIGTERM handler: %s\n",
 		g_strerror (errno));
 
-  sigchld_nexus = g_object_new (META_TYPE_NEXUS, NULL);
-
-  sigchld_signal_id =
-    g_signal_new ("sigchld", META_TYPE_NEXUS,
-                  G_SIGNAL_RUN_LAST,
-                  0, NULL, NULL,
-                  g_cclosure_marshal_VOID__UINT_POINTER,
-                  G_TYPE_NONE,
-                  2,
-                  G_TYPE_UINT, G_TYPE_POINTER);
-  
-  act.sa_flags = SA_NOCLDSTOP | SA_SIGINFO;
-  act.sa_handler = SIG_DFL;
-  act.sa_sigaction = &sigchld_handler;
-  if (sigaction (SIGCHLD, &act, NULL) < 0)
-    g_printerr ("Failed to register SIGCHLD handler: %s\n",
-		g_strerror (errno));
-
   if (g_getenv ("MUTTER_VERBOSE"))
     meta_set_verbose (TRUE);
   if (g_getenv ("MUTTER_DEBUG"))

src/core/session.c

@@ -29,6 +29,7 @@
 #include <X11/Xatom.h>
 
 #include <time.h>
+#include <sys/wait.h>
 
 #ifndef HAVE_SM
 void
@@ -1749,11 +1750,11 @@ finish_interact (gboolean shutdown)
 }
 
 static void
-sigchld_handler (MetaNexus *nexus, guint arg1, gpointer arg2, gpointer user_data)
+dialog_closed (GPid pid, int status, gpointer user_data)
 {
   gboolean shutdown = GPOINTER_TO_INT (user_data);
 
-  if (arg1 == 0) /* pressed "OK" */
+  if (WIFEXITED (status) && WEXITSTATUS (status) == 0) /* pressed "OK" */
     {
       finish_interact (shutdown);
     }
@@ -1767,6 +1768,7 @@ warn_about_lame_clients_and_finish_interact (gboolean shutdown)
   GSList *lame_details = NULL;
   GSList *tmp;
   GSList *columns = NULL;
+  GPid pid;
   
   windows = meta_display_list_windows (meta_get_display (), META_LIST_DEFAULT);
   tmp = windows;
@@ -1814,7 +1816,7 @@ warn_about_lame_clients_and_finish_interact (gboolean shutdown)
     }
   g_slist_free (lame);
 
-  meta_show_dialog("--list",
+  pid = meta_show_dialog("--list",
                          _("These windows do not support &quot;save current setup&quot; "
                            "and will have to be restarted manually next time "
                            "you log in."),
@@ -1827,10 +1829,7 @@ warn_about_lame_clients_and_finish_interact (gboolean shutdown)
 
   g_slist_free (lame_details);
 
-  g_signal_connect (sigchld_nexus, "sigchld",
+  g_child_watch_add (pid, dialog_closed, GINT_TO_POINTER (shutdown));
-                    G_CALLBACK (sigchld_handler),
-                    GINT_TO_POINTER (shutdown));
-
 }
 
 #endif /* HAVE_SM */

src/core/util.c

@@ -40,8 +40,6 @@
 #include <X11/Xlib.h>   /* must explicitly be included for Solaris; #326746 */
 #include <X11/Xutil.h>  /* Just for the definition of the various gravities */
 
-MetaNexus *sigchld_nexus;
-
 #ifdef HAVE_BACKTRACE
 #include <execinfo.h>
 void
@@ -560,7 +558,7 @@ meta_show_dialog (const char *type,
   int i=0;
   GPid child_pid;
   const char **argvl = g_malloc(sizeof (char*) *
-                                (15 +
+                                (17 +
                                  g_slist_length (columns)*2 +
                                  g_slist_length (entries)));
 
@@ -568,6 +566,8 @@ meta_show_dialog (const char *type,
   argvl[i++] = type;
   argvl[i++] = "--screen";
   argvl[i++] = screen_number_text;
+  argvl[i++] = "--class";
+  argvl[i++] = "mutter-dialog";
   argvl[i++] = "--title";
   /* Translators: This is the title used on dialog boxes */
   argvl[i++] = _("Mutter");
@@ -641,31 +641,6 @@ meta_show_dialog (const char *type,
   return child_pid;
 }
 
-GType
-meta_nexus_get_type (void)
-{
-  static GType nexus_type = 0;
-
-  if (!nexus_type)
-    {
-      static const GTypeInfo nexus_info =
-      {
-        sizeof (MetaNexusClass),
-	NULL, NULL, NULL, NULL, NULL,
-	sizeof (MetaNexus),
-	0,
-	NULL, NULL
-      };
-
-      nexus_type = g_type_register_static (G_TYPE_OBJECT,
-					   "MetaNexus",
-					   &nexus_info,
-					   0);
-    }
-
-  return nexus_type;
-}
-
 /***************************************************************************
  * Later functions: like idles but integrated with the Clutter repaint loop
  ***************************************************************************/

src/include/util.h

@@ -131,36 +131,6 @@ GPid meta_show_dialog (const char *type,
 
 #endif /* !WITH_VERBOSE_MODE */
 
-#include <glib-object.h>
-
-#define META_TYPE_NEXUS            (meta_nexus_get_type ())
-#define META_NEXUS(obj)            (G_TYPE_CHECK_INSTANCE_CAST ((obj), META_TYPE_NEXUS, MetaNexus))
-#define META_NEXUS_CLASS(klass)    (G_TYPE_CHECK_CLASS_CAST ((klass), META_TYPE_NEXUS, MetaNexusClass))
-#define META_IS_NEXUS(obj)         (G_TYPE_CHECK_INSTANCE_TYPE ((obj), META_TYPE_NEXUS))
-#define META_IS_NEXUS_CLASS(klass) (G_TYPE_CHECK_CLASS_TYPE ((klass), META_TYPE_NEXUS))
-#define META_NEXUS_GET_CLASS(obj)  (G_TYPE_INSTANCE_GET_CLASS ((obj), META_TYPE_NEXUS, MetaNexusClass))
-
-typedef struct _MetaNexus
-{
-  GObject parent_instance;
-} MetaNexus;
-
-typedef struct _MetaNexusClass
-{
-  GObjectClass parent_class;
-} MetaNexusClass;
-
-GType meta_nexus_get_type (void) G_GNUC_CONST;
-MetaNexus *meta_nexus_new ();
-
-/**
- * An object which exists purely to attach signals to; this is to receive
- * signals when a child process exits.  The signal is "sigchld" with no detail.
- *
- * \bug Eventually we should have a specialised type for objects like these.
- */
-extern MetaNexus *sigchld_nexus;
-
 /**
  * MetaLaterType:
  * @META_LATER_RESIZE: call in a resize processing phase that is done