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     aio_context_set_poll_params(iothread->ctx, iothread->poll_max_ns, 0, 0,
 102                                 &local_error);
 103     if (local_error) {
 104         error_propagate(errp, local_error);
 105         aio_context_unref(iothread->ctx);
 106         iothread->ctx = NULL;
 107         return;
 108     }
 109
 110     qemu_mutex_init(&iothread->init_done_lock);
 111     qemu_cond_init(&iothread->init_done_cond);
 112
 113     /* This assumes we are called from a thread with useful CPU affinity for us
 114      * to inherit.
 115      */
 116     name = object_get_canonical_path_component(OBJECT(obj));
 117     thread_name = g_strdup_printf("IO %s", name);
 118     qemu_thread_create(&iothread->thread, thread_name, iothread_run,
 119                        iothread, QEMU_THREAD_JOINABLE);
 120     g_free(thread_name);
 121     g_free(name);
 122
 123     /* Wait for initialization to complete */
 124     qemu_mutex_lock(&iothread->init_done_lock);
 125     while (iothread->thread_id == -1) {
 126         qemu_cond_wait(&iothread->init_done_cond,
 127                        &iothread->init_done_lock);
 128     }
 129     qemu_mutex_unlock(&iothread->init_done_lock);
 130 }
 131
 132 static void iothread_get_poll_max_ns(Object *obj, Visitor *v,
 133         const char *name, void *opaque, Error **errp)
 134 {
 135     IOThread *iothread = IOTHREAD(obj);
 136
 137     visit_type_int64(v, name, &iothread->poll_max_ns, errp);
 138 }
 139
 140 static void iothread_set_poll_max_ns(Object *obj, Visitor *v,
 141         const char *name, void *opaque, Error **errp)
 142 {
 143     IOThread *iothread = IOTHREAD(obj);
 144     Error *local_err = NULL;
 145     int64_t value;
 146
 147     visit_type_int64(v, name, &value, &local_err);
 148     if (local_err) {
 149         goto out;
 150     }
 151
 152     if (value < 0) {
 153         error_setg(&local_err, "poll_max_ns value must be in range "
 154                    "[0, %"PRId64"]", INT64_MAX);
 155         goto out;
 156     }
 157
 158     iothread->poll_max_ns = value;
 159
 160     if (iothread->ctx) {
 161         aio_context_set_poll_params(iothread->ctx, value, 0, 0, &local_err);
 162     }
 163
 164 out:
 165     error_propagate(errp, local_err);
 166 }
 167
 168 static void iothread_class_init(ObjectClass *klass, void *class_data)
 169 {
 170     UserCreatableClass *ucc = USER_CREATABLE_CLASS(klass);
 171     ucc->complete = iothread_complete;
 172
 173     object_class_property_add(klass, "poll-max-ns", "int",
 174                               iothread_get_poll_max_ns,
 175                               iothread_set_poll_max_ns,
 176                               NULL, NULL, &error_abort);
 177 }
 178
 179 static const TypeInfo iothread_info = {
 180     .name = TYPE_IOTHREAD,
 181     .parent = TYPE_OBJECT,
 182     .class_init = iothread_class_init,
 183     .instance_size = sizeof(IOThread),
 184     .instance_finalize = iothread_instance_finalize,
 185     .interfaces = (InterfaceInfo[]) {
 186         {TYPE_USER_CREATABLE},
 187         {}
 188     },
 189 };
 190
 191 static void iothread_register_types(void)
 192 {
 193     type_register_static(&iothread_info);
 194 }
 195
 196 type_init(iothread_register_types)
 197
 198 char *iothread_get_id(IOThread *iothread)
 199 {
 200     return object_get_canonical_path_component(OBJECT(iothread));
 201 }
 202
 203 AioContext *iothread_get_aio_context(IOThread *iothread)
 204 {
 205     return iothread->ctx;
 206 }
 207
 208 static int query_one_iothread(Object *object, void *opaque)
 209 {
 210     IOThreadInfoList ***prev = opaque;
 211     IOThreadInfoList *elem;
 212     IOThreadInfo *info;
 213     IOThread *iothread;
 214
 215     iothread = (IOThread *)object_dynamic_cast(object, TYPE_IOTHREAD);
 216     if (!iothread) {
 217         return 0;
 218     }
 219
 220     info = g_new0(IOThreadInfo, 1);
 221     info->id = iothread_get_id(iothread);
 222     info->thread_id = iothread->thread_id;
 223
 224     elem = g_new0(IOThreadInfoList, 1);
 225     elem->value = info;
 226     elem->next = NULL;
 227
 228     **prev = elem;
 229     *prev = &elem->next;
 230     return 0;
 231 }
 232
 233 IOThreadInfoList *qmp_query_iothreads(Error **errp)
 234 {
 235     IOThreadInfoList *head = NULL;
 236     IOThreadInfoList **prev = &head;
 237     Object *container = object_get_objects_root();
 238
 239     object_child_foreach(container, query_one_iothread, &prev);
 240     return head;
 241 }
 242
 243 void iothread_stop_all(void)
 244 {
 245     Object *container = object_get_objects_root();
 246     BlockDriverState *bs;
 247     BdrvNextIterator it;
 248
 249     for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) {
 250         AioContext *ctx = bdrv_get_aio_context(bs);
 251         if (ctx == qemu_get_aio_context()) {
 252             continue;
 253         }
 254         aio_context_acquire(ctx);
 255         bdrv_set_aio_context(bs, qemu_get_aio_context());
 256         aio_context_release(ctx);
 257     }
 258
 259     object_child_foreach(container, iothread_stop, NULL);
 260 }