[gnome-software/1748-software-search-forever-loading-if-app-installing-or-uninstalling-in-parallel] flatpak: Avoid deadlock under gs_flatpak_refine_wildcard()

[Milan Crha <mcrha src gnome org>]

commit 3eed67fb8ab1cec6d3261c9c1cd9119acdffef0a
Author: Milan Crha <mcrha redhat com>
Date:   Mon Sep 5 12:01:46 2022 +0200

    flatpak: Avoid deadlock under gs_flatpak_refine_wildcard()
    
    The gs_flatpak_refine_wildcard() calls with a reader lock on the silo.
    That function calls gs_flatpak_refine_app_unlocked(), which calls
    ensure_flatpak_silo_with_locker(), which can request a writer lock
    due to invalidated silo, which causes the deadlock due to the held
    reader lock. Avoid it by propagating the reader lock up to the call
    stack and release it before the writer lock is requested.
    
    Closes https://gitlab.gnome.org/GNOME/gnome-software/-/issues/1748

 plugins/flatpak/gs-flatpak.c | 17 ++++++++++-------
 1 file changed, 10 insertions(+), 7 deletions(-)
---
diff --git a/plugins/flatpak/gs-flatpak.c b/plugins/flatpak/gs-flatpak.c
index 3f0f351e9..aac55b16d 100644
--- a/plugins/flatpak/gs-flatpak.c
+++ b/plugins/flatpak/gs-flatpak.c
@@ -3411,25 +3411,25 @@ gs_flatpak_refine_appstream (GsFlatpak *self,
        return TRUE;
 }
 
-/* the _unlocked() version doesn't call gs_flatpak_rescan_app_data,
- * in order to avoid taking the writer lock on self->silo_lock */
 static gboolean
 gs_flatpak_refine_app_unlocked (GsFlatpak *self,
                                 GsApp *app,
                                 GsPluginRefineFlags flags,
                                 gboolean interactive,
+                                GRWLockReaderLocker **locker,
                                 GCancellable *cancellable,
                                 GError **error)
 {
        GsAppState old_state = gs_app_get_state (app);
-       g_autoptr(GRWLockReaderLocker) locker = NULL;
        g_autoptr(GError) local_error = NULL;
 
        /* not us */
        if (gs_app_get_bundle_kind (app) != AS_BUNDLE_KIND_FLATPAK)
                return TRUE;
 
-       if (!ensure_flatpak_silo_with_locker (self, &locker, interactive, cancellable, error))
+       g_clear_pointer (locker, g_rw_lock_reader_locker_free);
+
+       if (!ensure_flatpak_silo_with_locker (self, locker, interactive, cancellable, error))
                return FALSE;
 
        /* always do AppStream properties */
@@ -3554,6 +3554,7 @@ gs_flatpak_refine_addons (GsFlatpak *self,
                          gboolean interactive,
                          GCancellable *cancellable)
 {
+       g_autoptr(GRWLockReaderLocker) locker = NULL;
        g_autoptr(GsAppList) addons = NULL;
        g_autoptr(GString) errors = NULL;
        guint ii, sz;
@@ -3571,7 +3572,7 @@ gs_flatpak_refine_addons (GsFlatpak *self,
                /* To have refined also the state  */
                gs_app_set_state (addon, GS_APP_STATE_UNKNOWN);
 
-               if (!gs_flatpak_refine_app_unlocked (self, addon, flags, interactive, cancellable, 
&local_error)) {
+               if (!gs_flatpak_refine_app_unlocked (self, addon, flags, interactive, &locker, cancellable, 
&local_error)) {
                        if (errors)
                                g_string_append_c (errors, '\n');
                        else
@@ -3601,11 +3602,13 @@ gs_flatpak_refine_app (GsFlatpak *self,
                       GCancellable *cancellable,
                       GError **error)
 {
+       g_autoptr(GRWLockReaderLocker) locker = NULL;
+
        /* ensure valid */
        if (!gs_flatpak_rescan_app_data (self, interactive, cancellable, error))
                return FALSE;
 
-       return gs_flatpak_refine_app_unlocked (self, app, flags, interactive, cancellable, error);
+       return gs_flatpak_refine_app_unlocked (self, app, flags, interactive, &locker, cancellable, error);
 }
 
 gboolean
@@ -3647,7 +3650,7 @@ gs_flatpak_refine_wildcard (GsFlatpak *self, GsApp *app,
                if (new == NULL)
                        return FALSE;
                gs_flatpak_claim_app (self, new);
-               if (!gs_flatpak_refine_app_unlocked (self, new, refine_flags, interactive, cancellable, 
error))
+               if (!gs_flatpak_refine_app_unlocked (self, new, refine_flags, interactive, &locker, 
cancellable, error))
                        return FALSE;
                gs_app_subsume_metadata (new, app);
                gs_app_list_add (list, new);