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 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 --- util/yank.c | 207 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 207 insertions(+) create mode 100644 util/yank.c (limited to 'util/yank.c') diff --git a/util/yank.c b/util/yank.c new file mode 100644 index 0000000000..fc08f65209 --- /dev/null +++ b/util/yank.c @@ -0,0 +1,207 @@ +/* + * 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. + */ + +#include "qemu/osdep.h" +#include "qapi/error.h" +#include "qemu/thread.h" +#include "qemu/queue.h" +#include "qemu/lockable.h" +#include "qapi/qapi-commands-yank.h" +#include "qapi/qapi-visit-yank.h" +#include "qapi/clone-visitor.h" +#include "io/channel.h" +#include "qemu/yank.h" + +struct YankFuncAndParam { + YankFn *func; + void *opaque; + QLIST_ENTRY(YankFuncAndParam) next; +}; + +struct YankInstanceEntry { + YankInstance *instance; + QLIST_HEAD(, YankFuncAndParam) yankfns; + QLIST_ENTRY(YankInstanceEntry) next; +}; + +typedef struct YankFuncAndParam YankFuncAndParam; +typedef struct YankInstanceEntry YankInstanceEntry; + +/* + * This lock protects the yank_instance_list below. Because it's taken by + * OOB-capable commands, it must be "fast", i.e. it may only be held for a + * bounded, short time. See docs/devel/qapi-code-gen.txt for additional + * information. + */ +static QemuMutex yank_lock; + +static QLIST_HEAD(, YankInstanceEntry) yank_instance_list + = QLIST_HEAD_INITIALIZER(yank_instance_list); + +static bool yank_instance_equal(const YankInstance *a, const YankInstance *b) +{ + if (a->type != b->type) { + return false; + } + + switch (a->type) { + case YANK_INSTANCE_TYPE_BLOCK_NODE: + return g_str_equal(a->u.block_node.node_name, + b->u.block_node.node_name); + + case YANK_INSTANCE_TYPE_CHARDEV: + return g_str_equal(a->u.chardev.id, b->u.chardev.id); + + case YANK_INSTANCE_TYPE_MIGRATION: + return true; + + default: + abort(); + } +} + +static YankInstanceEntry *yank_find_entry(const YankInstance *instance) +{ + YankInstanceEntry *entry; + + QLIST_FOREACH(entry, &yank_instance_list, next) { + if (yank_instance_equal(entry->instance, instance)) { + return entry; + } + } + return NULL; +} + +bool yank_register_instance(const YankInstance *instance, Error **errp) +{ + YankInstanceEntry *entry; + + QEMU_LOCK_GUARD(&yank_lock); + + if (yank_find_entry(instance)) { + error_setg(errp, "duplicate yank instance"); + return false; + } + + entry = g_new0(YankInstanceEntry, 1); + entry->instance = QAPI_CLONE(YankInstance, instance); + QLIST_INIT(&entry->yankfns); + QLIST_INSERT_HEAD(&yank_instance_list, entry, next); + + return true; +} + +void yank_unregister_instance(const YankInstance *instance) +{ + YankInstanceEntry *entry; + + QEMU_LOCK_GUARD(&yank_lock); + entry = yank_find_entry(instance); + assert(entry); + + assert(QLIST_EMPTY(&entry->yankfns)); + QLIST_REMOVE(entry, next); + qapi_free_YankInstance(entry->instance); + g_free(entry); +} + +void yank_register_function(const YankInstance *instance, + YankFn *func, + void *opaque) +{ + YankInstanceEntry *entry; + YankFuncAndParam *func_entry; + + QEMU_LOCK_GUARD(&yank_lock); + entry = yank_find_entry(instance); + assert(entry); + + func_entry = g_new0(YankFuncAndParam, 1); + func_entry->func = func; + func_entry->opaque = opaque; + + QLIST_INSERT_HEAD(&entry->yankfns, func_entry, next); +} + +void yank_unregister_function(const YankInstance *instance, + YankFn *func, + void *opaque) +{ + YankInstanceEntry *entry; + YankFuncAndParam *func_entry; + + QEMU_LOCK_GUARD(&yank_lock); + entry = yank_find_entry(instance); + assert(entry); + + QLIST_FOREACH(func_entry, &entry->yankfns, next) { + if (func_entry->func == func && func_entry->opaque == opaque) { + QLIST_REMOVE(func_entry, next); + g_free(func_entry); + return; + } + } + + abort(); +} + +void yank_generic_iochannel(void *opaque) +{ + QIOChannel *ioc = QIO_CHANNEL(opaque); + + qio_channel_shutdown(ioc, QIO_CHANNEL_SHUTDOWN_BOTH, NULL); +} + +void qmp_yank(YankInstanceList *instances, + Error **errp) +{ + YankInstanceList *tail; + YankInstanceEntry *entry; + YankFuncAndParam *func_entry; + + QEMU_LOCK_GUARD(&yank_lock); + for (tail = instances; tail; tail = tail->next) { + entry = yank_find_entry(tail->value); + if (!entry) { + error_set(errp, ERROR_CLASS_DEVICE_NOT_FOUND, "Instance not found"); + return; + } + } + for (tail = instances; tail; tail = tail->next) { + entry = yank_find_entry(tail->value); + assert(entry); + QLIST_FOREACH(func_entry, &entry->yankfns, next) { + func_entry->func(func_entry->opaque); + } + } +} + +YankInstanceList *qmp_query_yank(Error **errp) +{ + YankInstanceEntry *entry; + YankInstanceList *ret; + + ret = NULL; + + QEMU_LOCK_GUARD(&yank_lock); + QLIST_FOREACH(entry, &yank_instance_list, next) { + YankInstanceList *new_entry; + new_entry = g_new0(YankInstanceList, 1); + new_entry->value = QAPI_CLONE(YankInstance, entry->instance); + new_entry->next = ret; + ret = new_entry; + } + + return ret; +} + +static void __attribute__((__constructor__)) yank_init(void) +{ + qemu_mutex_init(&yank_lock); +} -- cgit v1.2.3