[dsme] Avoid recursion during dsmesock disconnecting. Fixes JB#38474

Using availability of dsme dbus service as an trigger for disconnecting
also the dsmesock connection creates a shutdown time hazard where mce
attempts to recursively deactivate process watchdog on an already closed
connection.

As dsme dropping from systembus no longer means that dsme is about to
exit, do not trigger dsmesock disconnects when dsme service loses name
owner on system bus.

Avoid recursive process watchdog quits during disconnect by doing the
quitting only once / connect after removal of socket io watch.

Drop reconnect attempts on I/O error situations as they are unlikely
to do any good and can lead to further recursive behavior.

Do not initiate new dsmesock connections while device is shutting down.

Signed-off-by: Simo Piiroinen <simo.piiroinen@jollamobile.com>

mce-dsme.c

@@ -123,7 +123,6 @@ static gboolean       mce_dsme_socket_recv_cb      (GIOChannel *source, GIOCondi
 static bool           mce_dsme_socket_is_connected (void);
 static bool           mce_dsme_socket_connect      (void);
 static void           mce_dsme_socket_disconnect   (void);
-static void           mce_dsme_socket_reconnect    (void);
 
 /* ------------------------------------------------------------------------- *
  * DBUS_HANDLERS
@@ -558,6 +557,10 @@ static void mce_dsme_set_shutting_down(bool shutting_down)
     mce_log(LL_DEVEL, "Shutdown %s",
             mce_dsme_shutting_down_flag ? "started" : "canceled");
 
+    /* Re-evaluate dsmesock connection */
+    if( !mce_dsme_shutting_down_flag )
+        mce_dsme_socket_connect();
+
     execute_datapipe(&shutting_down_pipe,
                      GINT_TO_POINTER(mce_dsme_shutting_down_flag),
                      USE_INDATA, CACHE_INDATA);
@@ -588,10 +591,6 @@ static bool mce_dsme_socket_send(gpointer msg, const char *request_name)
     if( dsmesock_send(mce_dsme_socket_connection, msg) == -1) {
         mce_log(LL_ERR, "failed to send %s to dsme; %m",
                 request_name);
-
-        /* close and try to re-connect */
-        mce_dsme_socket_reconnect();
-        goto EXIT;
     }
 
     mce_log(LL_DEBUG, "%s sent to DSME", request_name);
@@ -688,8 +687,17 @@ static bool mce_dsme_socket_connect(void)
 {
     GIOChannel *iochan = NULL;
 
-    /* Make sure we start from closed state */
-    mce_dsme_socket_disconnect();
+    /* No new connections during shutdown */
+    if( mce_dsme_is_shutting_down() )
+        goto EXIT;
+
+    /* No new connections unless dsme dbus service is up */
+    if( dsme_available != SERVICE_STATE_RUNNING )
+        goto EXIT;
+
+    /* Already connected ? */
+    if( mce_dsme_socket_recv_id )
+        goto EXIT;
 
     mce_log(LL_DEBUG, "Opening DSME socket");
 
@@ -721,39 +729,32 @@ static bool mce_dsme_socket_connect(void)
 EXIT:
     if( iochan ) g_io_channel_unref(iochan);
 
+    if( !mce_dsme_socket_recv_id )
+        mce_dsme_socket_disconnect();
+
     return mce_dsme_socket_is_connected();
 }
 
 /** Close dsmesock connection
  */
 static void mce_dsme_socket_disconnect(void)
 {
-    if( mce_dsme_socket_is_connected() )
-        mce_dsme_processwd_quit();
-
     if( mce_dsme_socket_recv_id ) {
         mce_log(LL_DEBUG, "Removing DSME socket notifier");
         g_source_remove(mce_dsme_socket_recv_id);
         mce_dsme_socket_recv_id = 0;
+
+        /* Still having had a live socket notifier means: We have
+         * initiated the dsmesock disconnect and need to deactivate
+         * the process watchdog before actually disconnecting. */
+        mce_dsme_processwd_quit();
     }
 
     if( mce_dsme_socket_connection ) {
         mce_log(LL_DEBUG, "Closing DSME socket");
         dsmesock_close(mce_dsme_socket_connection);
         mce_dsme_socket_connection = 0;
     }
-
-    // FIXME: should we assume something about the system state?
-}
-
-/** Close dsmesock connection and reconnect if/when dsme is available
- */
-static void mce_dsme_socket_reconnect(void)
-{
-    mce_dsme_socket_disconnect();
-
-    if( dsme_available == SERVICE_STATE_RUNNING )
-        mce_dsme_socket_connect();
 }
 
 /* ========================================================================= *
@@ -896,10 +897,9 @@ static void mce_dsme_datapipe_dsme_available_cb(gconstpointer const data)
             service_state_repr(prev),
             service_state_repr(dsme_available));
 
+    /* Re-evaluate dsmesock connection */
     if( dsme_available == SERVICE_STATE_RUNNING )
         mce_dsme_socket_connect();
-    else
-        mce_dsme_socket_disconnect();
 
 EXIT:
     return;
@@ -1035,9 +1035,6 @@ void mce_dsme_exit(void)
 
     mce_dsme_dbus_quit();
 
-    if( mce_dsme_socket_is_connected() )
-        mce_dsme_processwd_quit();
-
     mce_dsme_socket_disconnect();
 
     mce_dsme_datapipe_quit();