[mutter/wip/carlosg/xwayland-non-fatal-io-errors: 76/76] wayland: Set IO error exit handler

[Carlos Garnacho <carlosg src gnome org>]

commit f4a1dcfc935598db2f396731a0d59fbf988c1237
Author: Carlos Garnacho <carlosg gnome org>
Date:   Fri Jun 14 16:04:44 2019 +0200

    wayland: Set IO error exit handler
    
    If this call is available, we can turn libX11 IO errors (fatal by definition)
    into something we can recover from. Try to dispose all X11 resources and close
    the display instead, so the compositor can survive the event.
    
    https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1447

 config.h.meson              |  3 +++
 meson.build                 |  8 ++++++++
 src/wayland/meta-xwayland.c | 17 +++++++++++++++++
 3 files changed, 28 insertions(+)
---
diff --git a/config.h.meson b/config.h.meson
index b2a23596f0..f4d6000e17 100644
--- a/config.h.meson
+++ b/config.h.meson
@@ -71,6 +71,9 @@
 /* Whether Xwayland has -initfd option */
 #mesondefine HAVE_XWAYLAND_INITFD
 
+/* Whether libX11 has XSetIOErrorExitHandler */
+#mesondefine HAVE_XSETIOERROREXITHANDLER
+
 /* Whether the mkostemp function exists */
 #mesondefine HAVE_MKOSTEMP
 
diff --git a/meson.build b/meson.build
index 885437931e..07b2d0066f 100644
--- a/meson.build
+++ b/meson.build
@@ -424,6 +424,13 @@ if have_wayland
   endif
 endif
 
+have_xsetioerrorexithandler = false
+if cc.has_function('XSetIOErrorExitHandler', dependencies: x11_dep,
+                   prefix: '''#include <X11/Xlib.h>''')
+  have_xsetioerrorexithandler = true
+  cdata.set('HAVE_XSETIOERROREXITHANDLER', 1)
+endif
+
 optional_functions = [
   'mkostemp',
   'posix_fallocate',
@@ -495,6 +502,7 @@ output = [
   '        Introspection............ ' + have_introspection.to_string(),
   '        Profiler................. ' + have_profiler.to_string(),
   '        Xwayland initfd.......... ' + have_xwayland_initfd.to_string(),
+  '        Safe X11 I/O errors...... ' + have_xsetioerrorexithandler.to_string(),
   '',
   '    Tests:',
   '',
diff --git a/src/wayland/meta-xwayland.c b/src/wayland/meta-xwayland.c
index 88a04e5a2c..f3dd192605 100644
--- a/src/wayland/meta-xwayland.c
+++ b/src/wayland/meta-xwayland.c
@@ -334,6 +334,20 @@ x_io_error (Display *display)
   return 0;
 }
 
+#ifdef HAVE_XSETIOERROREXITHANDLER
+static void
+x_io_error_exit (Display        *display,
+                 MetaX11Display *x11_display)
+{
+  MetaWaylandCompositor *compositor = meta_wayland_compositor_get_default ();
+  MetaXWaylandManager *manager = &compositor->xwayland_manager;
+
+  g_warning ("Xwayland just died, attempting to recover");
+  manager->xserver_grace_period_id =
+    g_idle_add (shutdown_xwayland_cb, manager);
+}
+#endif
+
 void
 meta_xwayland_override_display_number (int number)
 {
@@ -795,6 +809,9 @@ meta_xwayland_complete_init (MetaDisplay *display,
      we won't reset the tty).
   */
   XSetIOErrorHandler (x_io_error);
+#ifdef HAVE_XSETIOERROREXITHANDLER
+  XSetIOErrorExitHandler (xdisplay, x_io_error_exit, display);
+#endif
 
   g_signal_connect (display, "x11-display-closing",
                     G_CALLBACK (on_x11_display_closing), NULL);