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 "sysemu/iothread.h"
  20 #include "qmp-commands.h"
  21 #include "qemu/error-report.h"
  22 #include "qemu/rcu.h"
  23
  24 typedef ObjectClass IOThreadClass;
  25
  26 #define IOTHREAD_GET_CLASS(obj) \
  27    OBJECT_GET_CLASS(IOThreadClass, obj, TYPE_IOTHREAD)
  28 #define IOTHREAD_CLASS(klass) \
  29    OBJECT_CLASS_CHECK(IOThreadClass, klass, TYPE_IOTHREAD)
  30
  31 static void *iothread_run(void *opaque)
  32 {
  33     IOThread *iothread = opaque;
  34     bool blocking;
  35
  36     rcu_register_thread();
  37
  38     qemu_mutex_lock(&iothread->init_done_lock);
  39     iothread->thread_id = qemu_get_thread_id();
  40     qemu_cond_signal(&iothread->init_done_cond);
  41     qemu_mutex_unlock(&iothread->init_done_lock);
  42
  43     while (!iothread->stopping) {
  44         aio_context_acquire(iothread->ctx);
  45         blocking = true;
  46         while (!iothread->stopping && aio_poll(iothread->ctx, blocking)) {
  47             /* Progress was made, keep going */
  48             blocking = false;
  49         }
  50         aio_context_release(iothread->ctx);
  51     }
  52
  53     rcu_unregister_thread();
  54     return NULL;
  55 }
  56
  57 static void iothread_instance_finalize(Object *obj)
  58 {
  59     IOThread *iothread = IOTHREAD(obj);
  60
  61     if (!iothread->ctx) {
  62         return;
  63     }
  64     iothread->stopping = true;
  65     aio_notify(iothread->ctx);
  66     qemu_thread_join(&iothread->thread);
  67     qemu_cond_destroy(&iothread->init_done_cond);
  68     qemu_mutex_destroy(&iothread->init_done_lock);
  69     aio_context_unref(iothread->ctx);
  70 }
  71
  72 static void iothread_complete(UserCreatable *obj, Error **errp)
  73 {
  74     Error *local_error = NULL;
  75     IOThread *iothread = IOTHREAD(obj);
  76     char *name, *thread_name;
  77
  78     iothread->stopping = false;
  79     iothread->thread_id = -1;
  80     iothread->ctx = aio_context_new(&local_error);
  81     if (!iothread->ctx) {
  82         error_propagate(errp, local_error);
  83         return;
  84     }
  85
  86     qemu_mutex_init(&iothread->init_done_lock);
  87     qemu_cond_init(&iothread->init_done_cond);
  88
  89     /* This assumes we are called from a thread with useful CPU affinity for us
  90      * to inherit.
  91      */
  92     name = object_get_canonical_path_component(OBJECT(obj));
  93     thread_name = g_strdup_printf("IO %s", name);
  94     qemu_thread_create(&iothread->thread, thread_name, iothread_run,
  95                        iothread, QEMU_THREAD_JOINABLE);
  96     g_free(thread_name);
  97     g_free(name);
  98
  99     /* Wait for initialization to complete */
 100     qemu_mutex_lock(&iothread->init_done_lock);
 101     while (iothread->thread_id == -1) {
 102         qemu_cond_wait(&iothread->init_done_cond,
 103                        &iothread->init_done_lock);
 104     }
 105     qemu_mutex_unlock(&iothread->init_done_lock);
 106 }
 107
 108 static void iothread_class_init(ObjectClass *klass, void *class_data)
 109 {
 110     UserCreatableClass *ucc = USER_CREATABLE_CLASS(klass);
 111     ucc->complete = iothread_complete;
 112 }
 113
 114 static const TypeInfo iothread_info = {
 115     .name = TYPE_IOTHREAD,
 116     .parent = TYPE_OBJECT,
 117     .class_init = iothread_class_init,
 118     .instance_size = sizeof(IOThread),
 119     .instance_finalize = iothread_instance_finalize,
 120     .interfaces = (InterfaceInfo[]) {
 121         {TYPE_USER_CREATABLE},
 122         {}
 123     },
 124 };
 125
 126 static void iothread_register_types(void)
 127 {
 128     type_register_static(&iothread_info);
 129 }
 130
 131 type_init(iothread_register_types)
 132
 133 char *iothread_get_id(IOThread *iothread)
 134 {
 135     return object_get_canonical_path_component(OBJECT(iothread));
 136 }
 137
 138 AioContext *iothread_get_aio_context(IOThread *iothread)
 139 {
 140     return iothread->ctx;
 141 }
 142
 143 static int query_one_iothread(Object *object, void *opaque)
 144 {
 145     IOThreadInfoList ***prev = opaque;
 146     IOThreadInfoList *elem;
 147     IOThreadInfo *info;
 148     IOThread *iothread;
 149
 150     iothread = (IOThread *)object_dynamic_cast(object, TYPE_IOTHREAD);
 151     if (!iothread) {
 152         return 0;
 153     }
 154
 155     info = g_new0(IOThreadInfo, 1);
 156     info->id = iothread_get_id(iothread);
 157     info->thread_id = iothread->thread_id;
 158
 159     elem = g_new0(IOThreadInfoList, 1);
 160     elem->value = info;
 161     elem->next = NULL;
 162
 163     **prev = elem;
 164     *prev = &elem->next;
 165     return 0;
 166 }
 167
 168 IOThreadInfoList *qmp_query_iothreads(Error **errp)
 169 {
 170     IOThreadInfoList *head = NULL;
 171     IOThreadInfoList **prev = &head;
 172     Object *container = object_get_objects_root();
 173
 174     object_child_foreach(container, query_one_iothread, &prev);
 175     return head;
 176 }