The yank feature allows to recover from hanging qemu by "yanking"
at various parts. Other qemu systems can register themselves and
multiple yank functions. Then all yank functions for selected
instances can be called by the 'yank' out-of-band qmp command.
Available instances can be queried by a 'query-yank' oob command.
Signed-off-by: Lukas Straub
Acked-by: Stefan Hajnoczi
---
include/qemu/yank.h | 95 +++
qapi/meson.build | 1 +
qapi/qapi-schema.json | 1 +
qapi/yank.json| 115 ++
util/meson.build | 1 +
util/yank.c | 216 ++
6 files changed, 429 insertions(+)
create mode 100644 include/qemu/yank.h
create mode 100644 qapi/yank.json
create mode 100644 util/yank.c
diff --git a/include/qemu/yank.h b/include/qemu/yank.h
new file mode 100644
index 00..96f5b2626f
--- /dev/null
+++ b/include/qemu/yank.h
@@ -0,0 +1,95 @@
+/*
+ * QEMU yank feature
+ *
+ * Copyright (c) Lukas Straub
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#ifndef YANK_H
+#define YANK_H
+
+#include "qapi/qapi-types-yank.h"
+
+typedef void (YankFn)(void *opaque);
+
+/**
+ * yank_register_instance: Register a new instance.
+ *
+ * This registers a new instance for yanking. Must be called before any yank
+ * function is registered for this instance.
+ *
+ * This function is thread-safe.
+ *
+ * @instance: The instance.
+ * @errp: Error object.
+ */
+void yank_register_instance(const YankInstance *instance, Error **errp);
+
+/**
+ * yank_unregister_instance: Unregister a instance.
+ *
+ * This unregisters a instance. Must be called only after every yank function
+ * of the instance has been unregistered.
+ *
+ * This function is thread-safe.
+ *
+ * @instance: The instance.
+ */
+void yank_unregister_instance(const YankInstance *instance);
+
+/**
+ * yank_register_function: Register a yank function
+ *
+ * This registers a yank function. All limitations of qmp oob commands apply
+ * to the yank function as well. See docs/devel/qapi-code-gen.txt under
+ * "An OOB-capable command handler must satisfy the following conditions".
+ *
+ * This function is thread-safe.
+ *
+ * @instance: The instance.
+ * @func: The yank function.
+ * @opaque: Will be passed to the yank function.
+ */
+void yank_register_function(const YankInstance *instance,
+YankFn *func,
+void *opaque);
+
+/**
+ * yank_unregister_function: Unregister a yank function
+ *
+ * This unregisters a yank function.
+ *
+ * This function is thread-safe.
+ *
+ * @instance: The instance.
+ * @func: func that was passed to yank_register_function.
+ * @opaque: opaque that was passed to yank_register_function.
+ */
+void yank_unregister_function(const YankInstance *instance,
+ YankFn *func,
+ void *opaque);
+
+/**
+ * yank_generic_iochannel: Generic yank function for iochannel
+ *
+ * This is a generic yank function which will call qio_channel_shutdown on the
+ * provided QIOChannel.
+ *
+ * @opaque: QIOChannel to shutdown
+ */
+void yank_generic_iochannel(void *opaque);
+
+#define BLOCKDEV_YANK_INSTANCE(the_node_name) (&(YankInstance) { \
+.type = YANK_INSTANCE_TYPE_BLOCK_NODE, \
+.u.block_node.node_name = (the_node_name) })
+
+#define CHARDEV_YANK_INSTANCE(the_id) (&(YankInstance) { \
+.type = YANK_INSTANCE_TYPE_CHARDEV, \
+.u.chardev.id = (the_id) })
+
+#define MIGRATION_YANK_INSTANCE (&(YankInstance) { \
+.type = YANK_INSTANCE_TYPE_MIGRATION })
+
+#endif
diff --git a/qapi/meson.build b/qapi/meson.build
index 0e98146f1f..ab68e7900e 100644
--- a/qapi/meson.build
+++ b/qapi/meson.build
@@ -47,6 +47,7 @@ qapi_all_modules = [
'trace',
'transaction',
'ui',
+ 'yank',
]
qapi_storage_daemon_modules = [
diff --git a/qapi/qapi-schema.json b/qapi/qapi-schema.json
index 0b444b76d2..79c1705ed7 100644
--- a/qapi/qapi-schema.json
+++ b/qapi/qapi-schema.json
@@ -91,3 +91,4 @@
{ 'include': 'audio.json' }
{ 'include': 'acpi.json' }
{ 'include': 'pci.json' }
+{ 'include': 'yank.json' }
diff --git a/qapi/yank.json b/qapi/yank.json
new file mode 100644
index 00..1964a2202e
--- /dev/null
+++ b/qapi/yank.json
@@ -0,0 +1,115 @@
+# -*- Mode: Python -*-
+# vim: filetype=python
+#
+
+##
+# @YankInstanceType:
+#
+# An enumeration of yank instance types. See @YankInstance for more
+# information.
+#
+# Since: 5.2
+##
+{ 'enum': 'YankInstanceType',
+ 'data': [ 'block-node', 'chardev', 'migration' ] }
+
+##
+# @YankInstanceBlockNode:
+#
+# Specifies which block graph node to yank. See @YankInstance for more
+# information.
+#
+# @node-name: the name of the block graph node
+#
+# Since: 5.2
+##
+{ 'struct': 'YankInstanceBlockNode',
+ 'data': { 'node-name': 'str' } }
+
+##
+# @YankInstanceChardev:
+#
+# Specifies which
