From 50186051f425da3ace2425371c5271d0b64e7122 Mon Sep 17 00:00:00 2001 From: Lukas Straub Date: Mon, 28 Dec 2020 16:08:41 +0100 Subject: Introduce yank feature 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 Reviewed-by: Markus Armbruster Message-Id: <69934ceacfd33a7dfe53db145ecc630ad39ee47c.1609167865.git.lukasstraub2@web.de> Acked-by: Marc-André Lureau Signed-off-by: Markus Armbruster --- include/qemu/yank.h | 97 +++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 97 insertions(+) create mode 100644 include/qemu/yank.h (limited to 'include') diff --git a/include/qemu/yank.h b/include/qemu/yank.h new file mode 100644 index 0000000000..5b93c70cbf --- /dev/null +++ b/include/qemu/yank.h @@ -0,0 +1,97 @@ +/* + * 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. + * + * Returns true on success or false if an error occured. + */ +bool 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 -- cgit v1.2.3-55-g7522 From 8659f317d3303092d8e534eeefd160aa5ead9aab Mon Sep 17 00:00:00 2001 From: Lukas Straub Date: Mon, 28 Dec 2020 16:08:59 +0100 Subject: io: Document qmp oob suitability of qio_channel_shutdown and io_shutdown Migration and yank code assume that qio_channel_shutdown is thread -safe and can be called from qmp oob handler. Document this after checking the code. Signed-off-by: Lukas Straub Acked-by: Stefan Hajnoczi Reviewed-by: Daniel P. Berrangé Message-Id: <32b8c27e256da043f0f00db05bd7ab8fbc506070.1609167865.git.lukasstraub2@web.de> Signed-off-by: Markus Armbruster --- include/io/channel.h | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) (limited to 'include') diff --git a/include/io/channel.h b/include/io/channel.h index 4d6fe45f63..ab9ea77959 100644 --- a/include/io/channel.h +++ b/include/io/channel.h @@ -92,7 +92,8 @@ struct QIOChannel { * provide additional optional features. * * Consult the corresponding public API docs for a description - * of the semantics of each callback + * of the semantics of each callback. io_shutdown in particular + * must be thread-safe, terminate quickly and must not block. */ struct QIOChannelClass { ObjectClass parent; @@ -510,6 +511,8 @@ int qio_channel_close(QIOChannel *ioc, * QIO_CHANNEL_FEATURE_SHUTDOWN prior to calling * this method. * + * This function is thread-safe, terminates quickly and does not block. + * * Returns: 0 on success, -1 on error */ int qio_channel_shutdown(QIOChannel *ioc, -- cgit v1.2.3-55-g7522