Fix bug #353450 - Crash on quit during save.

Add a lock to the QofSession object, and use it in qof_session_save() to 
protect against re-entrance.

The lock always starts at 1 and is 0 while inside qof_session_save().  
If another call is made to qof_session_save() while one is in progress, 
the lock will momentarily drop below 0 before returning to zero.

Note: The per-session nature of the lock would make it appear that we support
concurrent saving of different sessions.  In fact, we do not, because the 
file backend blocks the main process until the forked gzip process is 
finished, and it only knows how to keep track of one child pid at a time. 



git-svn-id: svn+ssh://svn.gnucash.org/repo/gnucash/trunk@15168 57a11ea4-9604-0410-9ed3-97b8803252fd

lib/libqof/qof/qofsession-p.h

@@ -63,6 +63,7 @@ struct _QofSession
   /* Pointer to the backend that is actually used to move data
    * between the persistant store and the local engine.  */
   QofBackend *backend;
+  gint lock;
 };
 
 

lib/libqof/qof/qofsession.c

@@ -197,6 +197,7 @@ qof_session_init (QofSession *session)
   session->books = g_list_append (NULL, qof_book_new ());
   session->book_id = NULL;
   session->backend = NULL;
+  session->lock = 1;
 
   qof_session_clear_error (session);
 }
@@ -1193,8 +1194,10 @@ qof_session_save (QofSession *session,
 	int err;
 	gint num;
 	char *msg, *book_id;
-	
+
 	if (!session) return;
+	if (!g_atomic_int_dec_and_test(&session->lock))
+	    goto leave;
 	ENTER ("sess=%p book_id=%s", 
 		 session, session->book_id ? session->book_id : "(null)");
 	/* Partial book handling. */
@@ -1260,7 +1263,7 @@ qof_session_save (QofSession *session,
 						session->book_id = NULL;
 						qof_session_push_error (session, err, msg);
 						LEAVE("changed backend error %d", err);
-						return;
+						goto leave;
 					}
 					if (msg != NULL) 
 					{
@@ -1280,11 +1283,11 @@ qof_session_save (QofSession *session,
 				p = p->next;
 			}
 		}
-		if(!session->backend) 
+		if(!session->backend)
 		{
 			msg = g_strdup_printf("failed to load backend");
 			qof_session_push_error(session, ERR_BACKEND_NO_HANDLER, msg);
-			return;
+			goto leave;
 		}
 	}
 	/* If there is a backend, and the backend is reachable
@@ -1308,7 +1311,8 @@ qof_session_save (QofSession *session,
 			if (be->sync)
 			{
 				(be->sync)(be, abook);
-				if (save_error_handler(be, session)) return;
+				if (save_error_handler(be, session)) 
+                                    goto leave;
 			}
 		}
 		/* If we got to here, then the backend saved everything 
@@ -1316,7 +1320,7 @@ qof_session_save (QofSession *session,
 		/* Return the book_id to previous value. */
 		qof_session_clear_error (session);
 		LEAVE("Success");
-		return;
+		goto leave;
 	}
 	else
 	{
@@ -1324,9 +1328,17 @@ qof_session_save (QofSession *session,
 		qof_session_push_error(session, ERR_BACKEND_NO_HANDLER, msg);
 	}
 	LEAVE("error -- No backend!");
+ leave:
+	g_atomic_int_inc(&session->lock);
+	return;
 }
 
 /* ====================================================================== */
+gboolean
+qof_session_save_in_progress(QofSession *session)
+{
+    return (session && g_atomic_int_get(&session->lock) != 1);
+}
 
 void
 qof_session_end (QofSession *session)

lib/libqof/qof/qofsession.h

@@ -222,6 +222,7 @@ const char * qof_session_get_url (QofSession *session);
  *    if any data in the session hasn't been saved to long-term storage.
  */
 gboolean qof_session_not_saved(QofSession *session);
+gboolean qof_session_save_in_progress(QofSession *session);
 
 /** Allows the backend to warn the user if a dataset already exists. */
 gboolean qof_session_save_may_clobber_data (QofSession *session);