File PackageKit-cancel-transaction-if-daemon-disappe... of Package PackageKit.20954

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File PackageKit-cancel-transaction-if-daemon-disappears.patch of Package PackageKit.20954

From b2452c2d0023aad6be0751f9785e20f34bed6887 Mon Sep 17 00:00:00 2001
From: Philip Withnall <pwithnall@endlessos.org>
Date: Fri, 19 Mar 2021 22:43:16 +0000
Subject: [PATCH 1/2] packagekit-glib2: Cancel a transaction if the daemon
 disappears
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Most of the time, when using a `GDBusProxy`, and the service you’re
talking to disappears, you’ll get notified — the async D-Bus call you’re
making will return an error. However, due to PackageKit’s design for
handling long-running operations, there are long periods between a
transaction being created, and emitting its `Finished` signal, when no
D-Bus calls are pending.

If the daemon crashes during one of these periods, there is currently no
way for the packagekit-glib2 client code to notice until it tries to
make another D-Bus call on the same `GDBusProxy` instance, and that
might never happen — it might wait for the `Finished` signal forever.

Avoid that by connecting to `notify::g-name-owner`, which is emitted on
`GDBusProxy` if the daemon crashes. It changes value from the unique
name of the service, to `NULL`. When that happens, abort the transaction
state in the client with an error.

This should stop gnome-software hanging indefinitely if PackageKit
crashes during a transaction. In particular, if this happens a few times
during consecutive refresh operations, gnome-software can eventually run
out of worker threads, and become unresponsive entirely. (See
https://gitlab.gnome.org/GNOME/gnome-software/-/issues/1118.) The same
will likely be true of other clients which use packagekit-glib2.

Equivalent changes don’t seem to be needed in `pk-control.c` (which also
uses `GDBusProxy`), because all of its D-Bus operations appear to
maintain no state outside of individual method calls.

Signed-off-by: Philip Withnall <pwithnall@endlessos.org>
---
 lib/packagekit-glib2/pk-client.c | 31 ++++++++++++++++++++++++++++++-
 1 file changed, 30 insertions(+), 1 deletion(-)

diff --git a/lib/packagekit-glib2/pk-client.c b/lib/packagekit-glib2/pk-client.c
index 3f7d5230d..67df1c5ea 100644
--- a/lib/packagekit-glib2/pk-client.c
+++ b/lib/packagekit-glib2/pk-client.c
@@ -122,6 +122,9 @@ typedef struct {
 	PkClientHelper			*client_helper;
 } PkClientState;
 
+static void
+pk_client_state_finish (PkClientState *state,
+                        const GError  *error);
 static void
 pk_client_properties_changed_cb (GDBusProxy *proxy,
 				 GVariant *changed_properties,
@@ -133,6 +136,10 @@ pk_client_signal_cb (GDBusProxy *proxy,
 		     const gchar *signal_name,
 		     GVariant *parameters,
 		     gpointer user_data);
+static void
+pk_client_notify_name_owner_cb (GObject    *obj,
+                                GParamSpec *pspec,
+                                gpointer    user_data);
 
 /**
  * pk_client_error_quark:
@@ -662,6 +669,9 @@ pk_client_state_finish (PkClientState *state, const GError *error)
 		g_signal_handlers_disconnect_by_func (state->proxy,
 						      G_CALLBACK (pk_client_signal_cb),
 						      state);
+		g_signal_handlers_disconnect_by_func (state->proxy,
+						      G_CALLBACK (pk_client_notify_name_owner_cb),
+						      state);
 		g_object_unref (G_OBJECT (state->proxy));
 	}
 
@@ -1389,6 +1399,19 @@ pk_client_signal_cb (GDBusProxy *proxy,
 		return;
 }
 
+static void
+pk_client_notify_name_owner_cb (GObject *obj,
+				GParamSpec *pspec,
+				gpointer user_data)
+{
+	PkClientState *state = (PkClientState *) user_data;
+	g_autoptr(GError) local_error = NULL;
+
+	local_error = g_error_new_literal (PK_CLIENT_ERROR, PK_CLIENT_ERROR_FAILED,
+					   "PackageKit daemon disappeared");
+	pk_client_state_finish (state, local_error);
+}
+
 /*
  * pk_client_proxy_connect:
  **/
@@ -1416,6 +1439,9 @@ pk_client_proxy_connect (PkClientState *state)
 	g_signal_connect (state->proxy, "g-signal",
 			  G_CALLBACK (pk_client_signal_cb),
 			  state);
+	g_signal_connect (state->proxy, "notify::g-name-owner",
+			  G_CALLBACK (pk_client_notify_name_owner_cb),
+			  state);
 }
 
 /*
@@ -1440,7 +1466,7 @@ pk_client_method_cb (GObject *source_object,
 		return;
 	}
 
-	/* wait for ::Finished() */
+	/* wait for ::Finished() or notify::g-name-owner (if the daemon disappears) */
 }
 
 /*
@@ -4551,6 +4577,9 @@ pk_client_get_progress_state_finish (PkClientState *state, const GError *error)
 		g_signal_handlers_disconnect_by_func (state->proxy,
 						      G_CALLBACK (pk_client_signal_cb),
 						      state);
+		g_signal_handlers_disconnect_by_func (state->proxy,
+						      G_CALLBACK (pk_client_notify_name_owner_cb),
+						      state);
 		g_object_unref (G_OBJECT (state->proxy));
 	}
 
-- 
2.30.2

From 7c5fbc921b83321f3e1e56fe24ab1d0840de35ab Mon Sep 17 00:00:00 2001
From: Philip Withnall <pwithnall@endlessos.org>
Date: Fri, 19 Mar 2021 22:51:01 +0000
Subject: [PATCH 2/2] packagekit-glib2: Cancel a transaction if calling Cancel
 fails

If calling the `Cancel()` D-Bus method on a transaction fails, cancel
the client-side state anyway, to prevent the client from waiting forever
on a response which is unlikely to come.

Spotted in https://gitlab.gnome.org/GNOME/gnome-software/-/issues/1118.

Signed-off-by: Philip Withnall <pwithnall@endlessos.org>
---
 lib/packagekit-glib2/pk-client.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/lib/packagekit-glib2/pk-client.c b/lib/packagekit-glib2/pk-client.c
index 67df1c5ea..eba4ee47d 100644
--- a/lib/packagekit-glib2/pk-client.c
+++ b/lib/packagekit-glib2/pk-client.c
@@ -569,14 +569,18 @@ pk_client_cancel_cb (GObject *source_object,
 		     gpointer user_data)
 {
 	GDBusProxy *proxy = G_DBUS_PROXY (source_object);
+	PkClientState *state = user_data;
 	g_autoptr(GError) error = NULL;
 	g_autoptr(GVariant) value = NULL;
 
 	/* get the result */
 	value = g_dbus_proxy_call_finish (proxy, res, &error);
 	if (value == NULL) {
-		/* there's not really a lot we can do here */
-		g_warning ("failed to cancel: %s", error->message);
+		/* Instructing the daemon to cancel failed, so just return an
+		 * error to the client so they don’t wait forever. */
+		g_debug ("failed to cancel: %s", error->message);
+		g_prefix_error (&error, "Failed to cancel: ");
+		pk_client_state_finish (state, error);
 		return;
 	}
 }
@@ -600,7 +604,7 @@ pk_client_cancellable_cancel_cb (GCancellable *cancellable, PkClientState *state
 			   G_DBUS_CALL_FLAGS_NONE,
 			   PK_CLIENT_DBUS_METHOD_TIMEOUT,
 			   NULL,
-			   pk_client_cancel_cb, NULL);
+			   pk_client_cancel_cb, state);
 }
 
 /*
-- 
2.30.2

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File PackageKit-cancel-transaction-if-daemon-disappears.patch of Package PackageKit.20954

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