io: change the QIOTask callback signature

Currently the QIOTaskFunc signature takes an Object * for
the source, and an Error * for any error. We also need to
be able to provide a result pointer. Rather than continue
to add parameters to QIOTaskFunc, remove the existing
ones and simply pass the QIOTask object instead. This
has methods to access all the other data items required
in the callback impl.

Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>

15 files changed, 110 insertions, 112 deletions

diff --git a/include/io/task.h b/include/io/task.h
index 47daba961b..ad90970491 100644
--- a/include/io/task.h
+++ b/include/io/task.h
@@ -26,8 +26,7 @@
 
 typedef struct QIOTask QIOTask;
 
-typedef void (*QIOTaskFunc)(Object *source,
-                            Error *err,
+typedef void (*QIOTaskFunc)(QIOTask *task,
                             gpointer opaque);
 
 typedef int (*QIOTaskWorker)(QIOTask *task,
@@ -44,7 +43,7 @@ typedef int (*QIOTaskWorker)(QIOTask *task,
  * a public API which accepts a task callback:
  *
  * <example>
- *   <title>Task callback function signature</title>
+ *   <title>Task function signature</title>
  *   <programlisting>
  *  void myobject_operation(QMyObject *obj,
  *                          QIOTaskFunc *func,
@@ -57,12 +56,36 @@ typedef int (*QIOTaskWorker)(QIOTask *task,
  * is data to pass to it. The optional 'notify' function is used
  * to free 'opaque' when no longer needed.
  *
- * Now, lets say the implementation of this method wants to set
- * a timer to run once a second checking for completion of some
- * activity. It would do something like
+ * When the operation completes, the 'func' callback will be
+ * invoked, allowing the calling code to determine the result
+ * of the operation. An example QIOTaskFunc implementation may
+ * look like
  *
  * <example>
- *   <title>Task callback function implementation</title>
+ *   <title>Task callback implementation</title>
+ *   <programlisting>
+ *  static void myobject_operation_notify(QIOTask *task,
+ *                                        gpointer opaque)
+ *  {
+ *      Error *err = NULL;
+ *      if (qio_task_propagate_error(task, &err)) {
+ *          ...deal with the failure...
+ *          error_free(err);
+ *      } else {
+ *          QMyObject *src = QMY_OBJECT(qio_task_get_source(task));
+ *          ...deal with the completion...
+ *      }
+ *  }
+ *   </programlisting>
+ * </example>
+ *
+ * Now, lets say the implementation of the method using the
+ * task wants to set a timer to run once a second checking
+ * for completion of some activity. It would do something
+ * like
+ *
+ * <example>
+ *   <title>Task function implementation</title>
  *   <programlisting>
  *    void myobject_operation(QMyObject *obj,
  *                            QIOTaskFunc *func,
@@ -102,8 +125,8 @@ typedef int (*QIOTaskWorker)(QIOTask *task,
  *
  *      ...check something important...
  *       if (err) {
- *           qio_task_abort(task, err);
- *           error_free(task);
+ *           qio_task_set_error(task, err);
+ *           qio_task_complete(task);
  *           return FALSE;
  *       } else if (...work is completed ...) {
  *           qio_task_complete(task);
@@ -115,6 +138,10 @@ typedef int (*QIOTaskWorker)(QIOTask *task,
  *   </programlisting>
  * </example>
  *
+ * The 'qio_task_complete' call in this method will trigger
+ * the callback func 'myobject_operation_notify' shown
+ * earlier to deal with the results.
+ *
  * Once this function returns false, object_unref will be called
  * automatically on the task causing it to be released and the
  * ref on QMyObject dropped too.
@@ -187,8 +214,8 @@ typedef int (*QIOTaskWorker)(QIOTask *task,
  * 'err' attribute in the task object to determine if
  * the operation was successful or not.
  *
- * The returned task will be released when one of
- * qio_task_abort() or qio_task_complete() are invoked.
+ * The returned task will be released when qio_task_complete()
+ * is invoked.
  *
  * Returns: the task struct
  */
@@ -204,10 +231,8 @@ QIOTask *qio_task_new(Object *source,
  * @opaque: opaque data to pass to @worker
  * @destroy: function to free @opaque
  *
- * Run a task in a background thread. If @worker
- * returns 0 it will call qio_task_complete() in
- * the main event thread context. If @worker
- * returns -1 it will call qio_task_abort() in
+ * Run a task in a background thread. When @worker
+ * returns it will call qio_task_complete() in
  * the main event thread context.
  */
 void qio_task_run_in_thread(QIOTask *task,
@@ -219,25 +244,11 @@ void qio_task_run_in_thread(QIOTask *task,
  * qio_task_complete:
  * @task: the task struct
  *
- * Mark the operation as successfully completed
- * and free the memory for @task.
+ * Invoke the completion callback for @task and
+ * then free its memory.
  */
 void qio_task_complete(QIOTask *task);
 
-/**
- * qio_task_abort:
- * @task: the task struct
- * @err: the error to record for the operation
- *
- * Mark the operation as failed, with @err providing
- * details about the failure. The @err may be freed
- * afer the function returns, as the notification
- * callback is invoked synchronously. The @task will
- * be freed when this call completes.
- */
-void qio_task_abort(QIOTask *task,
-                    Error *err);
-
 
 /**
  * qio_task_set_error:
diff --git a/io/channel-tls.c b/io/channel-tls.c
index cf3bcca7ed..f25ab0ae53 100644
--- a/io/channel-tls.c
+++ b/io/channel-tls.c
@@ -153,8 +153,9 @@ static void qio_channel_tls_handshake_task(QIOChannelTLS *ioc,
 
     if (qcrypto_tls_session_handshake(ioc->session, &err) < 0) {
         trace_qio_channel_tls_handshake_fail(ioc);
-        qio_task_abort(task, err);
-        goto cleanup;
+        qio_task_set_error(task, err);
+        qio_task_complete(task);
+        return;
     }
 
     status = qcrypto_tls_session_get_handshake_status(ioc->session);
@@ -163,10 +164,10 @@ static void qio_channel_tls_handshake_task(QIOChannelTLS *ioc,
         if (qcrypto_tls_session_check_credentials(ioc->session,
                                                   &err) < 0) {
             trace_qio_channel_tls_credentials_deny(ioc);
-            qio_task_abort(task, err);
-            goto cleanup;
+            qio_task_set_error(task, err);
+        } else {
+            trace_qio_channel_tls_credentials_allow(ioc);
         }
-        trace_qio_channel_tls_credentials_allow(ioc);
         qio_task_complete(task);
     } else {
         GIOCondition condition;
@@ -183,9 +184,6 @@ static void qio_channel_tls_handshake_task(QIOChannelTLS *ioc,
                               task,
                               NULL);
     }
-
- cleanup:
-    error_free(err);
 }
 
 
diff --git a/io/channel-websock.c b/io/channel-websock.c
index f45bced82a..e47279a1ae 100644
--- a/io/channel-websock.c
+++ b/io/channel-websock.c
@@ -279,8 +279,8 @@ static gboolean qio_channel_websock_handshake_send(QIOChannel *ioc,
 
     if (ret < 0) {
         trace_qio_channel_websock_handshake_fail(ioc);
-        qio_task_abort(task, err);
-        error_free(err);
+        qio_task_set_error(task, err);
+        qio_task_complete(task);
         return FALSE;
     }
 
@@ -307,8 +307,8 @@ static gboolean qio_channel_websock_handshake_io(QIOChannel *ioc,
     ret = qio_channel_websock_handshake_read(wioc, &err);
     if (ret < 0) {
         trace_qio_channel_websock_handshake_fail(ioc);
-        qio_task_abort(task, err);
-        error_free(err);
+        qio_task_set_error(task, err);
+        qio_task_complete(task);
         return FALSE;
     }
     if (ret == 0) {
diff --git a/io/task.c b/io/task.c
index 1394e05200..42e1a75586 100644
--- a/io/task.c
+++ b/io/task.c
@@ -87,13 +87,11 @@ static gboolean gio_task_thread_result(gpointer opaque)
     struct QIOTaskThreadData *data = opaque;
 
     trace_qio_task_thread_result(data->task);
-    if (data->ret == 0) {
-        qio_task_complete(data->task);
-    } else {
-        qio_task_abort(data->task, data->err);
+    if (data->err) {
+        qio_task_set_error(data->task, data->err);
     }
+    qio_task_complete(data->task);
 
-    error_free(data->err);
     if (data->destroy) {
         data->destroy(data->opaque);
     }
@@ -149,19 +147,11 @@ void qio_task_run_in_thread(QIOTask *task,
 
 void qio_task_complete(QIOTask *task)
 {
-    task->func(task->source, NULL, task->opaque);
+    task->func(task, task->opaque);
     trace_qio_task_complete(task);
     qio_task_free(task);
 }
 
-void qio_task_abort(QIOTask *task,
-                    Error *err)
-{
-    task->func(task->source, err, task->opaque);
-    trace_qio_task_abort(task);
-    qio_task_free(task);
-}
-
 
 void qio_task_set_error(QIOTask *task,
                         Error *err)
diff --git a/io/trace-events b/io/trace-events
index e31b596ca1..ff993bef45 100644
--- a/io/trace-events
+++ b/io/trace-events
@@ -3,7 +3,6 @@
 # io/task.c
 qio_task_new(void *task, void *source, void *func, void *opaque) "Task new task=%p source=%p func=%p opaque=%p"
 qio_task_complete(void *task) "Task complete task=%p"
-qio_task_abort(void *task) "Task abort task=%p"
 qio_task_thread_start(void *task, void *worker, void *opaque) "Task thread start task=%p worker=%p opaque=%p"
 qio_task_thread_run(void *task) "Task thread run task=%p"
 qio_task_thread_exit(void *task) "Task thread exit task=%p"
diff --git a/migration/socket.c b/migration/socket.c
index 11f80b119b..13966f1d26 100644
--- a/migration/socket.c
+++ b/migration/socket.c
@@ -70,22 +70,23 @@ static void socket_connect_data_free(void *opaque)
     g_free(data);
 }
 
-static void socket_outgoing_migration(Object *src,
-                                      Error *err,
+static void socket_outgoing_migration(QIOTask *task,
                                       gpointer opaque)
 {
     struct SocketConnectData *data = opaque;
-    QIOChannel *sioc = QIO_CHANNEL(src);
+    QIOChannel *sioc = QIO_CHANNEL(qio_task_get_source(task));
+    Error *err = NULL;
 
-    if (err) {
+    if (qio_task_propagate_error(task, &err)) {
         trace_migration_socket_outgoing_error(error_get_pretty(err));
         data->s->to_dst_file = NULL;
         migrate_fd_error(data->s, err);
+        error_free(err);
     } else {
         trace_migration_socket_outgoing_connected(data->hostname);
         migration_channel_connect(data->s, sioc, data->hostname);
     }
-    object_unref(src);
+    object_unref(OBJECT(sioc));
 }
 
 static void socket_start_outgoing_migration(MigrationState *s,
diff --git a/migration/tls.c b/migration/tls.c
index 49ca9a8930..203c11d025 100644
--- a/migration/tls.c
+++ b/migration/tls.c
@@ -61,15 +61,15 @@ migration_tls_get_creds(MigrationState *s,
 }
 
 
-static void migration_tls_incoming_handshake(Object *src,
-                                             Error *err,
+static void migration_tls_incoming_handshake(QIOTask *task,
                                              gpointer opaque)
 {
-    QIOChannel *ioc = QIO_CHANNEL(src);
+    QIOChannel *ioc = QIO_CHANNEL(qio_task_get_source(task));
+    Error *err = NULL;
 
-    if (err) {
+    if (qio_task_propagate_error(task, &err)) {
         trace_migration_tls_incoming_handshake_error(error_get_pretty(err));
-        error_report("%s", error_get_pretty(err));
+        error_report_err(err);
     } else {
         trace_migration_tls_incoming_handshake_complete();
         migration_channel_process_incoming(migrate_get_current(), ioc);
@@ -107,17 +107,18 @@ void migration_tls_channel_process_incoming(MigrationState *s,
 }
 
 
-static void migration_tls_outgoing_handshake(Object *src,
-                                             Error *err,
+static void migration_tls_outgoing_handshake(QIOTask *task,
                                              gpointer opaque)
 {
     MigrationState *s = opaque;
-    QIOChannel *ioc = QIO_CHANNEL(src);
+    QIOChannel *ioc = QIO_CHANNEL(qio_task_get_source(task));
+    Error *err = NULL;
 
-    if (err) {
+    if (qio_task_propagate_error(task, &err)) {
         trace_migration_tls_outgoing_handshake_error(error_get_pretty(err));
         s->to_dst_file = NULL;
         migrate_fd_error(s, err);
+        error_free(err);
     } else {
         trace_migration_tls_outgoing_handshake_complete();
         migration_channel_connect(s, ioc, NULL);
diff --git a/nbd/common.c b/nbd/common.c
index b583a4f4cf..a5f39ea58e 100644
--- a/nbd/common.c
+++ b/nbd/common.c
@@ -78,15 +78,13 @@ ssize_t nbd_wr_syncv(QIOChannel *ioc,
 }
 
 
-void nbd_tls_handshake(Object *src,
-                       Error *err,
+void nbd_tls_handshake(QIOTask *task,
                        void *opaque)
 {
     struct NBDTLSHandshakeData *data = opaque;
 
-    if (err) {
-        TRACE("TLS failed %s", error_get_pretty(err));
-        data->error = error_copy(err);
+    if (qio_task_propagate_error(task, &data->error)) {
+        TRACE("TLS failed %s", error_get_pretty(data->error));
     }
     data->complete = true;
     g_main_loop_quit(data->loop);
diff --git a/nbd/nbd-internal.h b/nbd/nbd-internal.h
index eee20abc25..f43d990a05 100644
--- a/nbd/nbd-internal.h
+++ b/nbd/nbd-internal.h
@@ -120,8 +120,7 @@ struct NBDTLSHandshakeData {
 };
 
 
-void nbd_tls_handshake(Object *src,
-                       Error *err,
+void nbd_tls_handshake(QIOTask *task,
                        void *opaque);
 
 #endif
diff --git a/qemu-char.c b/qemu-char.c
index 676944a765..d8da1677ff 100644
--- a/qemu-char.c
+++ b/qemu-char.c
@@ -3277,14 +3277,13 @@ static void tcp_chr_telnet_init(CharDriverState *chr)
 }
 
 
-static void tcp_chr_tls_handshake(Object *source,
-                                  Error *err,
+static void tcp_chr_tls_handshake(QIOTask *task,
                                   gpointer user_data)
 {
     CharDriverState *chr = user_data;
     TCPCharDriver *s = chr->opaque;
 
-    if (err) {
+    if (qio_task_propagate_error(task, NULL)) {
         tcp_chr_disconnect(chr);
     } else {
         if (s->do_telnetopt) {
@@ -3492,20 +3491,23 @@ static void tcp_chr_free(CharDriverState *chr)
 }
 
 
-static void qemu_chr_socket_connected(Object *src, Error *err, void *opaque)
+static void qemu_chr_socket_connected(QIOTask *task, void *opaque)
 {
-    QIOChannelSocket *sioc = QIO_CHANNEL_SOCKET(src);
+    QIOChannelSocket *sioc = QIO_CHANNEL_SOCKET(qio_task_get_source(task));
     CharDriverState *chr = opaque;
     TCPCharDriver *s = chr->opaque;
+    Error *err = NULL;
 
-    if (err) {
+    if (qio_task_propagate_error(task, &err)) {
         check_report_connect_error(chr, err);
-        object_unref(src);
-        return;
+        error_free(err);
+        goto cleanup;
     }
 
     s->connect_err_reported = false;
     tcp_chr_new_client(chr, sioc);
+
+ cleanup:
     object_unref(OBJECT(sioc));
 }
 
diff --git a/tests/test-io-channel-socket.c b/tests/test-io-channel-socket.c
index aa88c3cf45..aaa9116fb7 100644
--- a/tests/test-io-channel-socket.c
+++ b/tests/test-io-channel-socket.c
@@ -156,12 +156,11 @@ struct TestIOChannelData {
 };
 
 
-static void test_io_channel_complete(Object *src,
-                                     Error *err,
+static void test_io_channel_complete(QIOTask *task,
                                      gpointer opaque)
 {
     struct TestIOChannelData *data = opaque;
-    data->err = err != NULL;
+    data->err = qio_task_propagate_error(task, NULL);
     g_main_loop_quit(data->loop);
 }
 
diff --git a/tests/test-io-channel-tls.c b/tests/test-io-channel-tls.c
index bd3ae2bf7a..8eaa208e1b 100644
--- a/tests/test-io-channel-tls.c
+++ b/tests/test-io-channel-tls.c
@@ -53,14 +53,13 @@ struct QIOChannelTLSHandshakeData {
     bool failed;
 };
 
-static void test_tls_handshake_done(Object *source,
-                                    Error *err,
+static void test_tls_handshake_done(QIOTask *task,
                                     gpointer opaque)
 {
     struct QIOChannelTLSHandshakeData *data = opaque;
 
     data->finished = true;
-    data->failed = err != NULL;
+    data->failed = qio_task_propagate_error(task, NULL);
 }
 
 
diff --git a/tests/test-io-task.c b/tests/test-io-task.c
index 024eb585e4..84144c9047 100644
--- a/tests/test-io-task.c
+++ b/tests/test-io-task.c
@@ -50,14 +50,13 @@ struct TestTaskData {
 };
 
 
-static void task_callback(Object *source,
-                          Error *err,
+static void task_callback(QIOTask *task,
                           gpointer opaque)
 {
     struct TestTaskData *data = opaque;
 
-    data->source = source;
-    data->err = err;
+    data->source = qio_task_get_source(task);
+    qio_task_propagate_error(task, &data->err);
 }
 
 
@@ -120,9 +119,9 @@ static void test_task_failure(void)
 
     error_setg(&err, "Some error");
 
-    qio_task_abort(task, err);
+    qio_task_set_error(task, err);
+    qio_task_complete(task);
 
-    error_free(err);
     object_unref(obj);
 
     g_assert(data.source == obj);
@@ -158,14 +157,13 @@ static int test_task_thread_worker(QIOTask *task,
 }
 
 
-static void test_task_thread_callback(Object *source,
-                                      Error *err,
+static void test_task_thread_callback(QIOTask *task,
                                       gpointer opaque)
 {
     struct TestThreadWorkerData *data = opaque;
 
-    data->source = source;
-    data->err = err;
+    data->source = qio_task_get_source(task);
+    qio_task_propagate_error(task, &data->err);
 
     data->complete = g_thread_self();
 
diff --git a/ui/vnc-auth-vencrypt.c b/ui/vnc-auth-vencrypt.c
index c0c29a5119..ffaab57550 100644
--- a/ui/vnc-auth-vencrypt.c
+++ b/ui/vnc-auth-vencrypt.c
@@ -65,16 +65,17 @@ static void start_auth_vencrypt_subauth(VncState *vs)
     }
 }
 
-static void vnc_tls_handshake_done(Object *source,
-                                   Error *err,
+static void vnc_tls_handshake_done(QIOTask *task,
                                    gpointer user_data)
 {
     VncState *vs = user_data;
+    Error *err = NULL;
 
-    if (err) {
+    if (qio_task_propagate_error(task, &err)) {
         VNC_DEBUG("Handshake failed %s\n",
                   error_get_pretty(err));
         vnc_client_error(vs);
+        error_free(err);
     } else {
         vs->ioc_tag = qio_channel_add_watch(
             vs->ioc, G_IO_IN | G_IO_OUT, vnc_client_io, vs, NULL);
diff --git a/ui/vnc-ws.c b/ui/vnc-ws.c
index bffb484a8d..f530cd5474 100644
--- a/ui/vnc-ws.c
+++ b/ui/vnc-ws.c
@@ -24,15 +24,16 @@
 #include "io/channel-websock.h"
 #include "qemu/bswap.h"
 
-static void vncws_tls_handshake_done(Object *source,
-                                     Error *err,
+static void vncws_tls_handshake_done(QIOTask *task,
                                      gpointer user_data)
 {
     VncState *vs = user_data;
+    Error *err = NULL;
 
-    if (err) {
+    if (qio_task_propagate_error(task, &err)) {
         VNC_DEBUG("Handshake failed %s\n", error_get_pretty(err));
         vnc_client_error(vs);
+        error_free(err);
     } else {
         VNC_DEBUG("TLS handshake complete, starting websocket handshake\n");
         vs->ioc_tag = qio_channel_add_watch(
@@ -83,15 +84,16 @@ gboolean vncws_tls_handshake_io(QIOChannel *ioc G_GNUC_UNUSED,
 }
 
 
-static void vncws_handshake_done(Object *source,
-                                 Error *err,
+static void vncws_handshake_done(QIOTask *task,
                                  gpointer user_data)
 {
     VncState *vs = user_data;
+    Error *err = NULL;
 
-    if (err) {
+    if (qio_task_propagate_error(task, &err)) {
         VNC_DEBUG("Websock handshake failed %s\n", error_get_pretty(err));
         vnc_client_error(vs);
+        error_free(err);
     } else {
         VNC_DEBUG("Websock handshake complete, starting VNC protocol\n");
         vnc_start_protocol(vs);