iothread.c

   1 /*
   2  * Event loop thread
   3  *
   4  * Copyright Red Hat Inc., 2013
   5  *
   6  * Authors:
   7  *  Stefan Hajnoczi   <stefanha@redhat.com>
   8  *
   9  * This work is licensed under the terms of the GNU GPL, version 2 or later.
  10  * See the COPYING file in the top-level directory.
  11  *
  12  */
  13
  14 #include "qemu/osdep.h"
  15 #include "qom/object.h"
  16 #include "qom/object_interfaces.h"
  17 #include "qemu/module.h"
  18 #include "block/aio.h"
  19 #include "block/block.h"
  20 #include "sysemu/iothread.h"
  21 #include "qmp-commands.h"
  22 #include "qemu/error-report.h"
  23 #include "qemu/rcu.h"
  24 #include "qemu/main-loop.h"
  25
  26 typedef ObjectClass IOThreadClass;
  27
  28 #define IOTHREAD_GET_CLASS(obj) \
  29    OBJECT_GET_CLASS(IOThreadClass, obj, TYPE_IOTHREAD)
  30 #define IOTHREAD_CLASS(klass) \
  31    OBJECT_CLASS_CHECK(IOThreadClass, klass, TYPE_IOTHREAD)
  32
  33 static __thread IOThread *my_iothread;
  34
  35 AioContext *qemu_get_current_aio_context(void)
  36 {
  37     return my_iothread ? my_iothread->ctx : qemu_get_aio_context();
  38 }
  39
  40 static void *iothread_run(void *opaque)
  41 {
  42     IOThread *iothread = opaque;
  43
  44     rcu_register_thread();
  45
  46     my_iothread = iothread;
  47     qemu_mutex_lock(&iothread->init_done_lock);
  48     iothread->thread_id = qemu_get_thread_id();
  49     qemu_cond_signal(&iothread->init_done_cond);
  50     qemu_mutex_unlock(&iothread->init_done_lock);
  51
  52     while (!atomic_read(&iothread->stopping)) {
  53         aio_poll(iothread->ctx, true);
  54     }
  55
  56     rcu_unregister_thread();
  57     return NULL;
  58 }
  59
  60 static int iothread_stop(Object *object, void *opaque)
  61 {
  62     IOThread *iothread;
  63
  64     iothread = (IOThread *)object_dynamic_cast(object, TYPE_IOTHREAD);
  65     if (!iothread || !iothread->ctx) {
  66         return 0;
  67     }
  68     iothread->stopping = true;
  69     aio_notify(iothread->ctx);
  70     qemu_thread_join(&iothread->thread);
  71     return 0;
  72 }
  73
  74 static void iothread_instance_finalize(Object *obj)
  75 {
  76     IOThread *iothread = IOTHREAD(obj);
  77
  78     iothread_stop(obj, NULL);
  79     qemu_cond_destroy(&iothread->init_done_cond);
  80     qemu_mutex_destroy(&iothread->init_done_lock);
  81     if (!iothread->ctx) {
  82         return;
  83     }
  84     aio_context_unref(iothread->ctx);
  85 }
  86
  87 static void iothread_complete(UserCreatable *obj, Error **errp)
  88 {
  89     Error *local_error = NULL;
  90     IOThread *iothread = IOTHREAD(obj);
  91     char *name, *thread_name;
  92
  93     iothread->stopping = false;
  94     iothread->thread_id = -1;
  95     iothread->ctx = aio_context_new(&local_error);
  96     if (!iothread->ctx) {
  97         error_propagate(errp, local_error);
  98         return;
  99     }
 100
 101     qemu_mutex_init(&iothread->init_done_lock);
 102     qemu_cond_init(&iothread->init_done_cond);
 103
 104     /* This assumes we are called from a thread with useful CPU affinity for us
 105      * to inherit.
 106      */
 107     name = object_get_canonical_path_component(OBJECT(obj));
 108     thread_name = g_strdup_printf("IO %s", name);
 109     qemu_thread_create(&iothread->thread, thread_name, iothread_run,
 110                        iothread, QEMU_THREAD_JOINABLE);
 111     g_free(thread_name);
 112     g_free(name);
 113
 114     /* Wait for initialization to complete */
 115     qemu_mutex_lock(&iothread->init_done_lock);
 116     while (iothread->thread_id == -1) {
 117         qemu_cond_wait(&iothread->init_done_cond,
 118                        &iothread->init_done_lock);
 119     }
 120     qemu_mutex_unlock(&iothread->init_done_lock);
 121 }
 122
 123 static void iothread_class_init(ObjectClass *klass, void *class_data)
 124 {
 125     UserCreatableClass *ucc = USER_CREATABLE_CLASS(klass);
 126     ucc->complete = iothread_complete;
 127 }
 128
 129 static const TypeInfo iothread_info = {
 130     .name = TYPE_IOTHREAD,
 131     .parent = TYPE_OBJECT,
 132     .class_init = iothread_class_init,
 133     .instance_size = sizeof(IOThread),
 134     .instance_finalize = iothread_instance_finalize,
 135     .interfaces = (InterfaceInfo[]) {
 136         {TYPE_USER_CREATABLE},
 137         {}
 138     },
 139 };
 140
 141 static void iothread_register_types(void)
 142 {
 143     type_register_static(&iothread_info);
 144 }
 145
 146 type_init(iothread_register_types)
 147
 148 char *iothread_get_id(IOThread *iothread)
 149 {
 150     return object_get_canonical_path_component(OBJECT(iothread));
 151 }
 152
 153 AioContext *iothread_get_aio_context(IOThread *iothread)
 154 {
 155     return iothread->ctx;
 156 }
 157
 158 static int query_one_iothread(Object *object, void *opaque)
 159 {
 160     IOThreadInfoList ***prev = opaque;
 161     IOThreadInfoList *elem;
 162     IOThreadInfo *info;
 163     IOThread *iothread;
 164
 165     iothread = (IOThread *)object_dynamic_cast(object, TYPE_IOTHREAD);
 166     if (!iothread) {
 167         return 0;
 168     }
 169
 170     info = g_new0(IOThreadInfo, 1);
 171     info->id = iothread_get_id(iothread);
 172     info->thread_id = iothread->thread_id;
 173
 174     elem = g_new0(IOThreadInfoList, 1);
 175     elem->value = info;
 176     elem->next = NULL;
 177
 178     **prev = elem;
 179     *prev = &elem->next;
 180     return 0;
 181 }
 182
 183 IOThreadInfoList *qmp_query_iothreads(Error **errp)
 184 {
 185     IOThreadInfoList *head = NULL;
 186     IOThreadInfoList **prev = &head;
 187     Object *container = object_get_objects_root();
 188
 189     object_child_foreach(container, query_one_iothread, &prev);
 190     return head;
 191 }
 192
 193 void iothread_stop_all(void)
 194 {
 195     Object *container = object_get_objects_root();
 196     BlockDriverState *bs;
 197     BdrvNextIterator it;
 198
 199     for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) {
 200         AioContext *ctx = bdrv_get_aio_context(bs);
 201         if (ctx == qemu_get_aio_context()) {
 202             continue;
 203         }
 204         aio_context_acquire(ctx);
 205         bdrv_set_aio_context(bs, qemu_get_aio_context());
 206         aio_context_release(ctx);
 207     }
 208
 209     object_child_foreach(container, iothread_stop, NULL);
 210 }