Merge "These changes are the raw update to qemu-2.6."

1 files changed, 255 insertions, 0 deletions

diff --git a/qemu/include/io/task.h b/qemu/include/io/task.h
new file mode 100644
index 000000000..2e69d8a47
--- /dev/null
+++ b/qemu/include/io/task.h
@@ -0,0 +1,255 @@
+/*
+ * QEMU I/O task
+ *
+ * Copyright (c) 2015 Red Hat, Inc.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#ifndef QIO_TASK_H__
+#define QIO_TASK_H__
+
+#include "qemu-common.h"
+#include "qom/object.h"
+
+typedef struct QIOTask QIOTask;
+
+typedef void (*QIOTaskFunc)(Object *source,
+                            Error *err,
+                            gpointer opaque);
+
+typedef int (*QIOTaskWorker)(QIOTask *task,
+                             Error **errp,
+                             gpointer opaque);
+
+/**
+ * QIOTask:
+ *
+ * The QIOTask object provides a simple mechanism for reporting
+ * success / failure of long running background operations.
+ *
+ * A object on which the operation is to be performed could have
+ * a public API which accepts a task callback:
+ *
+ * <example>
+ *   <title>Task callback function signature</title>
+ *   <programlisting>
+ *  void myobject_operation(QMyObject *obj,
+ *                          QIOTaskFunc *func,
+ *                          gpointer opaque,
+ *                          GDestroyNotify *notify);
+ *   </programlisting>
+ * </example>
+ *
+ * The 'func' parameter is the callback to be invoked, and 'opaque'
+ * 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
+ *
+ * <example>
+ *   <title>Task callback function implementation</title>
+ *   <programlisting>
+ *    void myobject_operation(QMyObject *obj,
+ *                            QIOTaskFunc *func,
+ *                            gpointer opaque,
+ *                            GDestroyNotify *notify)
+ *    {
+ *      QIOTask *task;
+ *
+ *      task = qio_task_new(OBJECT(obj), func, opaque, notify);
+ *
+ *      g_timeout_add_full(G_PRIORITY_DEFAULT,
+ *                         1000,
+ *                         myobject_operation_timer,
+ *                         task,
+ *                         NULL);
+ *    }
+ *   </programlisting>
+ * </example>
+ *
+ * It could equally have setup a watch on a file descriptor or
+ * created a background thread, or something else entirely.
+ * Notice that the source object is passed to the task, and
+ * QIOTask will hold a reference on that. This ensure that
+ * the QMyObject instance cannot be garbage collected while
+ * the async task is still in progress.
+ *
+ * In this case, myobject_operation_timer will fire after
+ * 3 secs and do
+ *
+ * <example>
+ *   <title>Task timer function</title>
+ *   <programlisting>
+ *   gboolean myobject_operation_timer(gpointer opaque)
+ *   {
+ *      QIOTask *task = QIO_TASK(opaque);
+ *      Error *err;*
+ *
+ *      ...check something important...
+ *       if (err) {
+ *           qio_task_abort(task, err);
+ *           error_free(task);
+ *           return FALSE;
+ *       } else if (...work is completed ...) {
+ *           qio_task_complete(task);
+ *           return FALSE;
+ *       }
+ *       ...carry on polling ...
+ *       return TRUE;
+ *   }
+ *   </programlisting>
+ * </example>
+ *
+ * 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.
+ *
+ * The QIOTask module can also be used to perform operations
+ * in a background thread context, while still reporting the
+ * results in the main event thread. This allows code which
+ * cannot easily be rewritten to be asychronous (such as DNS
+ * lookups) to be easily run non-blocking. Reporting the
+ * results in the main thread context means that the caller
+ * typically does not need to be concerned about thread
+ * safety wrt the QEMU global mutex.
+ *
+ * For example, the socket_listen() method will block the caller
+ * while DNS lookups take place if given a name, instead of IP
+ * address. The C library often do not provide a practical async
+ * DNS API, so the to get non-blocking DNS lookups in a portable
+ * manner requires use of a thread. So achieve a non-blocking
+ * socket listen using QIOTask would require:
+ *
+ * <example>
+ *    static int myobject_listen_worker(QIOTask *task,
+ *                                      Error **errp,
+ *                                      gpointer opaque)
+ *    {
+ *       QMyObject obj = QMY_OBJECT(qio_task_get_source(task));
+ *       SocketAddress *addr = opaque;
+ *
+ *       obj->fd = socket_listen(addr, errp);
+ *       if (obj->fd < 0) {
+ *          return -1;
+ *       }
+ *       return 0;
+ *    }
+ *
+ *    void myobject_listen_async(QMyObject *obj,
+ *                               SocketAddress *addr,
+ *                               QIOTaskFunc *func,
+ *                               gpointer opaque,
+ *                               GDestroyNotify *notify)
+ *    {
+ *      QIOTask *task;
+ *      SocketAddress *addrCopy;
+ *
+ *      qapi_copy_SocketAddress(&addrCopy, addr);
+ *      task = qio_task_new(OBJECT(obj), func, opaque, notify);
+ *
+ *      qio_task_run_in_thread(task, myobject_listen_worker,
+ *                             addrCopy,
+ *                             qapi_free_SocketAddress);
+ *    }
+ * </example>
+ *
+ * NB, The 'func' callback passed into myobject_listen_async
+ * will be invoked from the main event thread, despite the
+ * actual operation being performed in a different thread.
+ */
+
+/**
+ * qio_task_new:
+ * @source: the object on which the operation is invoked
+ * @func: the callback to invoke when the task completes
+ * @opaque: opaque data to pass to @func when invoked
+ * @destroy: optional callback to free @opaque
+ *
+ * Creates a new task struct to track completion of a
+ * background operation running on the object @source.
+ * When the operation completes or fails, the callback
+ * @func will be invoked. The callback can access the
+ * '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.
+ *
+ * Returns: the task struct
+ */
+QIOTask *qio_task_new(Object *source,
+                      QIOTaskFunc func,
+                      gpointer opaque,
+                      GDestroyNotify destroy);
+
+/**
+ * qio_task_run_in_thread:
+ * @task: the task struct
+ * @worker: the function to invoke in a thread
+ * @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
+ * the main event thread context.
+ */
+void qio_task_run_in_thread(QIOTask *task,
+                            QIOTaskWorker worker,
+                            gpointer opaque,
+                            GDestroyNotify destroy);
+
+/**
+ * qio_task_complete:
+ * @task: the task struct
+ *
+ * Mark the operation as succesfully completed
+ * and free the memory for @task.
+ */
+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_get_source:
+ * @task: the task struct
+ *
+ * Get the source object associated with the background
+ * task. This returns a new reference to the object,
+ * which the caller must released with object_unref()
+ * when no longer required.
+ *
+ * Returns: the source object
+ */
+Object *qio_task_get_source(QIOTask *task);
+
+#endif /* QIO_TASK_H__ */