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init: Move Meta main loop into JavaScript after GJS context is initialized

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gjs now has an internal mainloop that it can spin to resolve
module imports. That loop uses the thread default context,
so its possible that other sources, namely from mutter, get
dispatched when iterating the context. If that happens before
mutter is properly initialized, this will lead to a crash.

GjsContext needs to iterate its internal mainloop when initializing
to resolve internal modules, to avoid iterating Meta's mainloop and
triggering events before Meta is ready we will initialize the Shell
global and thus the GjsContext (js_context) before Meta.

Once GjsContext is initialized, we can call meta_context_setup().
Once Meta is setup and started, we'll run init.js which uses GJS'
internal promises API to set a "mainloop hook". The mainloop hook
is run immediately after the module returns so GJS will not attempt
to iterate the main loop again before exiting.

Also adjust the 'headlessStart' test to not wait for the
MetaContext::started signal, as that signal has now already
been emitted when the code is executed.

https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/6691

Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/2781>
This commit is contained in:
Evan Welsh 2023-06-07 08:58:08 -07:00 committed by Florian Müllner
parent 5d8e860a48
commit 8fb8f7f827
4 changed files with 79 additions and 63 deletions
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3
js/perf/headlessStart.js
View File

@ -23,8 +23,6 @@ function init() {
global.connect('shutdown', () => {
_testMonitor?.destroy();
});
global.context.connect('started',
() => {
GLib.timeout_add_seconds(
GLib.PRIORITY_LOW, 2,
() => {
@ -32,7 +30,6 @@ function init() {
_testMonitor = MetaTest.TestMonitor.new(
global.context, 1280, 720, 60.0);
});
});
Scripting.defineScriptEvent('monitorsChanged', 'Monitors changed');
const display = global.display;

19
js/ui/init.js
View File

@ -1,6 +1,25 @@
import {setConsoleLogDomain} from 'console';
import GLib from 'gi://GLib';
import {exit} from 'system';
setConsoleLogDomain('GNOME Shell');
imports.ui.environment.init();
// Run the Mutter main loop after
// GJS finishes resolving this module.
imports._promiseNative.setMainLoopHook(() => {
// Queue starting the shell
GLib.idle_add(GLib.PRIORITY_DEFAULT, () => {
try {
imports.ui.main.start();
} catch (e) {
logError(e);
exit(1);
}
return GLib.SOURCE_REMOVE;
});
// Run the meta context's main loop
global.context.run_main_loop();
});

27
src/gnome-shell-plugin.c
View File

@ -105,9 +105,6 @@ static void
gnome_shell_plugin_start (MetaPlugin *plugin)
{
GnomeShellPlugin *shell_plugin = GNOME_SHELL_PLUGIN (plugin);
GError *error = NULL;
uint8_t status;
GjsContext *gjs_context;
ClutterBackend *backend;
backend = clutter_get_default_backend ();
@ -123,30 +120,6 @@ gnome_shell_plugin_start (MetaPlugin *plugin)
shell_plugin->global = shell_global_get ();
_shell_global_set_plugin (shell_plugin->global, META_PLUGIN (shell_plugin));
gjs_context = _shell_global_get_gjs_context (shell_plugin->global);
if (!gjs_context_eval_module_file (gjs_context,
"resource:///org/gnome/shell/ui/init.js",
&status,
&error))
{
g_message ("Execution of main.js threw exception: %s", error->message);
g_error_free (error);
/* We just exit() here, since in a development environment you'll get the
* error in your shell output, and it's way better than a busted WM,
* which typically manifests as a white screen.
*
* In production, we shouldn't crash =) But if we do, we should get
* restarted by the session infrastructure, which is likely going
* to be better than some undefined state.
*
* If there was a generic "hook into bug-buddy for non-C crashes"
* infrastructure, here would be the place to put it.
*/
g_object_unref (gjs_context);
exit (1);
}
}
static ShellWM *

79
src/main.c
View File

@ -608,11 +608,8 @@ main (int argc, char **argv)
init_signal_handlers (context);
change_to_home_directory ();
if (!meta_context_setup (context, &error))
{
g_printerr ("Failed to setup: %s\n", error->message);
return EXIT_FAILURE;
}
if (session_mode == NULL)
session_mode = is_gdm_mode ? (char *)"gdm" : (char *)"user";
/* FIXME: Add gjs API to set this stuff and don't depend on the
* environment. These propagate to child processes.
@ -620,24 +617,6 @@ main (int argc, char **argv)
g_setenv ("GJS_DEBUG_OUTPUT", "stderr", TRUE);
g_setenv ("GJS_DEBUG_TOPICS", "JS ERROR;JS LOG", TRUE);
shell_init_debug (g_getenv ("SHELL_DEBUG"));
shell_dbus_init (meta_context_is_replacing (context));
shell_a11y_init ();
shell_perf_log_init ();
shell_introspection_init ();
shell_fonts_init ();
g_log_set_writer_func (default_log_writer, NULL, NULL);
/* Initialize the global object */
if (session_mode == NULL)
session_mode = is_gdm_mode ? (char *)"gdm" : (char *)"user";
_shell_global_init ("session-mode", session_mode,
"force-animations", force_animations,
NULL);
dump_gjs_stack_on_signal (SIGABRT);
dump_gjs_stack_on_signal (SIGFPE);
dump_gjs_stack_on_signal (SIGIOT);
@ -649,6 +628,33 @@ main (int argc, char **argv)
dump_gjs_stack_on_signal (SIGSEGV);
}
/* Initialize the Shell global, including GjsContext
* GjsContext will iterate the default main loop to
* resolve internal modules.
*/
_shell_global_init ("session-mode", session_mode,
"force-animations", force_animations,
NULL);
/* Setup Meta _after_ the Shell global to avoid GjsContext
* iterating on the main loop once Meta starts adding events
*/
if (!meta_context_setup (context, &error))
{
g_printerr ("Failed to setup: %s\n", error->message);
return EXIT_FAILURE;
}
shell_init_debug (g_getenv ("SHELL_DEBUG"));
shell_dbus_init (meta_context_is_replacing (context));
shell_a11y_init ();
shell_perf_log_init ();
shell_introspection_init ();
shell_fonts_init ();
g_log_set_writer_func (default_log_writer, NULL, NULL);
shell_profiler_init ();
if (meta_context_get_compositor_type (context) == META_COMPOSITOR_TYPE_WAYLAND)
@ -660,10 +666,31 @@ main (int argc, char **argv)
return EXIT_FAILURE;
}
if (!meta_context_run_main_loop (context, &error))
/* init.js calls meta_context_start_main_loop(), gjs_context_eval_module_file()
* will not return until Mutter is exited.
*/
GjsContext *gjs_context = _shell_global_get_gjs_context (shell_global_get());
uint8_t status;
if (!gjs_context_eval_module_file (gjs_context,
"resource:///org/gnome/shell/ui/init.js",
&status,
&error))
{
g_printerr ("GNOME Shell terminated with an error: %s\n", error->message);
ecode = EXIT_FAILURE;
g_message ("Execution of main.js threw exception: %s", error->message);
g_error_free (error);
/* We just exit() here, since in a development environment you'll get the
* error in your shell output, and it's way better than a busted WM,
* which typically manifests as a white screen.
*
* In production, we shouldn't crash =) But if we do, we should get
* restarted by the session infrastructure, which is likely going
* to be better than some undefined state.
*
* If there was a generic "hook into bug-buddy for non-C crashes"
* infrastructure, here would be the place to put it.
*/
g_object_unref (gjs_context);
exit (1);
}
g_message ("Shutting down GNOME Shell");