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