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     bool blocking;
  44
  45     rcu_register_thread();
  46
  47     my_iothread = iothread;
  48     qemu_mutex_lock(&iothread->init_done_lock);
  49     iothread->thread_id = qemu_get_thread_id();
  50     qemu_cond_signal(&iothread->init_done_cond);
  51     qemu_mutex_unlock(&iothread->init_done_lock);
  52
  53     while (!iothread->stopping) {
  54         aio_context_acquire(iothread->ctx);
  55         blocking = true;
  56         while (!iothread->stopping && aio_poll(iothread->ctx, blocking)) {
  57             /* Progress was made, keep going */
  58             blocking = false;
  59         }
  60         aio_context_release(iothread->ctx);
  61     }
  62
  63     rcu_unregister_thread();
  64     return NULL;
  65 }
  66
  67 static int iothread_stop(Object *object, void *opaque)
  68 {
  69     IOThread *iothread;
  70
  71     iothread = (IOThread *)object_dynamic_cast(object, TYPE_IOTHREAD);
  72     if (!iothread || !iothread->ctx) {
  73         return 0;
  74     }
  75     iothread->stopping = true;
  76     aio_notify(iothread->ctx);
  77     qemu_thread_join(&iothread->thread);
  78     return 0;
  79 }
  80
  81 static void iothread_instance_finalize(Object *obj)
  82 {
  83     IOThread *iothread = IOTHREAD(obj);
  84
  85     iothread_stop(obj, NULL);
  86     qemu_cond_destroy(&iothread->init_done_cond);
  87     qemu_mutex_destroy(&iothread->init_done_lock);
  88     if (!iothread->ctx) {
  89         return;
  90     }
  91     aio_context_unref(iothread->ctx);
  92 }
  93
  94 static void iothread_complete(UserCreatable *obj, Error **errp)
  95 {
  96     Error *local_error = NULL;
  97     IOThread *iothread = IOTHREAD(obj);
  98     char *name, *thread_name;
  99
 100     iothread->stopping = false;
 101     iothread->thread_id = -1;
 102     iothread->ctx = aio_context_new(&local_error);
 103     if (!iothread->ctx) {
 104         error_propagate(errp, local_error);
 105         return;
 106     }
 107
 108     qemu_mutex_init(&iothread->init_done_lock);
 109     qemu_cond_init(&iothread->init_done_cond);
 110
 111     /* This assumes we are called from a thread with useful CPU affinity for us
 112      * to inherit.
 113      */
 114     name = object_get_canonical_path_component(OBJECT(obj));
 115     thread_name = g_strdup_printf("IO %s", name);
 116     qemu_thread_create(&iothread->thread, thread_name, iothread_run,
 117                        iothread, QEMU_THREAD_JOINABLE);
 118     g_free(thread_name);
 119     g_free(name);
 120
 121     /* Wait for initialization to complete */
 122     qemu_mutex_lock(&iothread->init_done_lock);
 123     while (iothread->thread_id == -1) {
 124         qemu_cond_wait(&iothread->init_done_cond,
 125                        &iothread->init_done_lock);
 126     }
 127     qemu_mutex_unlock(&iothread->init_done_lock);
 128 }
 129
 130 static void iothread_class_init(ObjectClass *klass, void *class_data)
 131 {
 132     UserCreatableClass *ucc = USER_CREATABLE_CLASS(klass);
 133     ucc->complete = iothread_complete;
 134 }
 135
 136 static const TypeInfo iothread_info = {
 137     .name = TYPE_IOTHREAD,
 138     .parent = TYPE_OBJECT,
 139     .class_init = iothread_class_init,
 140     .instance_size = sizeof(IOThread),
 141     .instance_finalize = iothread_instance_finalize,
 142     .interfaces = (InterfaceInfo[]) {
 143         {TYPE_USER_CREATABLE},
 144         {}
 145     },
 146 };
 147
 148 static void iothread_register_types(void)
 149 {
 150     type_register_static(&iothread_info);
 151 }
 152
 153 type_init(iothread_register_types)
 154
 155 char *iothread_get_id(IOThread *iothread)
 156 {
 157     return object_get_canonical_path_component(OBJECT(iothread));
 158 }
 159
 160 AioContext *iothread_get_aio_context(IOThread *iothread)
 161 {
 162     return iothread->ctx;
 163 }
 164
 165 static int query_one_iothread(Object *object, void *opaque)
 166 {
 167     IOThreadInfoList ***prev = opaque;
 168     IOThreadInfoList *elem;
 169     IOThreadInfo *info;
 170     IOThread *iothread;
 171
 172     iothread = (IOThread *)object_dynamic_cast(object, TYPE_IOTHREAD);
 173     if (!iothread) {
 174         return 0;
 175     }
 176
 177     info = g_new0(IOThreadInfo, 1);
 178     info->id = iothread_get_id(iothread);
 179     info->thread_id = iothread->thread_id;
 180
 181     elem = g_new0(IOThreadInfoList, 1);
 182     elem->value = info;
 183     elem->next = NULL;
 184
 185     **prev = elem;
 186     *prev = &elem->next;
 187     return 0;
 188 }
 189
 190 IOThreadInfoList *qmp_query_iothreads(Error **errp)
 191 {
 192     IOThreadInfoList *head = NULL;
 193     IOThreadInfoList **prev = &head;
 194     Object *container = object_get_objects_root();
 195
 196     object_child_foreach(container, query_one_iothread, &prev);
 197     return head;
 198 }
 199
 200 void iothread_stop_all(void)
 201 {
 202     Object *container = object_get_objects_root();
 203     BlockDriverState *bs;
 204     BdrvNextIterator it;
 205
 206     for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) {
 207         AioContext *ctx = bdrv_get_aio_context(bs);
 208         if (ctx == qemu_get_aio_context()) {
 209             continue;
 210         }
 211         aio_context_acquire(ctx);
 212         bdrv_set_aio_context(bs, qemu_get_aio_context());
 213         aio_context_release(ctx);
 214     }
 215
 216     object_child_foreach(container, iothread_stop, NULL);
 217 }