mirror of https://gitee.com/openkylin/qemu.git
324 lines
9.9 KiB
C
324 lines
9.9 KiB
C
/*
|
|
* 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)(QIOTask *task,
|
|
gpointer opaque);
|
|
|
|
typedef void (*QIOTaskWorker)(QIOTask *task,
|
|
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 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.
|
|
*
|
|
* 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 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,
|
|
* 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_set_error(task, err);
|
|
* qio_task_complete(task);
|
|
* return FALSE;
|
|
* } else if (...work is completed ...) {
|
|
* qio_task_complete(task);
|
|
* return FALSE;
|
|
* }
|
|
* ...carry on polling ...
|
|
* return TRUE;
|
|
* }
|
|
* </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.
|
|
*
|
|
* 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 void myobject_listen_worker(QIOTask *task,
|
|
* gpointer opaque)
|
|
* {
|
|
* QMyObject obj = QMY_OBJECT(qio_task_get_source(task));
|
|
* SocketAddress *addr = opaque;
|
|
* Error *err = NULL;
|
|
*
|
|
* obj->fd = socket_listen(addr, &err);
|
|
*
|
|
qio_task_set_error(task, err);
|
|
* }
|
|
*
|
|
* void myobject_listen_async(QMyObject *obj,
|
|
* SocketAddress *addr,
|
|
* QIOTaskFunc *func,
|
|
* gpointer opaque,
|
|
* GDestroyNotify notify)
|
|
* {
|
|
* QIOTask *task;
|
|
* SocketAddress *addrCopy;
|
|
*
|
|
* addrCopy = QAPI_CLONE(SocketAddress, 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 qio_task_complete()
|
|
* is 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. When @worker
|
|
* returns it will call qio_task_complete() 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
|
|
*
|
|
* Invoke the completion callback for @task and
|
|
* then free its memory.
|
|
*/
|
|
void qio_task_complete(QIOTask *task);
|
|
|
|
|
|
/**
|
|
* qio_task_set_error:
|
|
* @task: the task struct
|
|
* @err: pointer to the error, or NULL
|
|
*
|
|
* Associate an error with the task, which can later
|
|
* be retrieved with the qio_task_propagate_error()
|
|
* method. This method takes ownership of @err, so
|
|
* it is not valid to access it after this call
|
|
* completes. If @err is NULL this is a no-op. If
|
|
* this is call multiple times, only the first
|
|
* provided @err will be recorded, later ones will
|
|
* be discarded and freed.
|
|
*/
|
|
void qio_task_set_error(QIOTask *task,
|
|
Error *err);
|
|
|
|
|
|
/**
|
|
* qio_task_propagate_error:
|
|
* @task: the task struct
|
|
* @errp: pointer to a NULL-initialized error object
|
|
*
|
|
* Propagate the error associated with @task
|
|
* into @errp.
|
|
*
|
|
* Returns: true if an error was propagated, false otherwise
|
|
*/
|
|
bool qio_task_propagate_error(QIOTask *task,
|
|
Error **errp);
|
|
|
|
|
|
/**
|
|
* qio_task_set_result_pointer:
|
|
* @task: the task struct
|
|
* @result: pointer to the result data
|
|
*
|
|
* Associate an opaque result with the task,
|
|
* which can later be retrieved with the
|
|
* qio_task_get_result_pointer() method
|
|
*
|
|
*/
|
|
void qio_task_set_result_pointer(QIOTask *task,
|
|
gpointer result,
|
|
GDestroyNotify notify);
|
|
|
|
|
|
/**
|
|
* qio_task_get_result_pointer:
|
|
* @task: the task struct
|
|
*
|
|
* Retrieve the opaque result data associated
|
|
* with the task, if any.
|
|
*
|
|
* Returns: the task result, or NULL
|
|
*/
|
|
gpointer qio_task_get_result_pointer(QIOTask *task);
|
|
|
|
|
|
/**
|
|
* qio_task_get_source:
|
|
* @task: the task struct
|
|
*
|
|
* Get the source object associated with the background
|
|
* task. The caller does not own a reference on the
|
|
* returned Object, and so should call object_ref()
|
|
* if it wants to keep the object pointer outside the
|
|
* lifetime of the QIOTask object.
|
|
*
|
|
* Returns: the source object
|
|
*/
|
|
Object *qio_task_get_source(QIOTask *task);
|
|
|
|
#endif /* QIO_TASK_H */
|