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
  76     iothread->stopping = false;
  77     iothread->thread_id = -1;
  78     iothread->ctx = aio_context_new(&local_error);
  79     if (!iothread->ctx) {
  80         error_propagate(errp, local_error);
  81         return;
  82     }
  83
  84     qemu_mutex_init(&iothread->init_done_lock);
  85     qemu_cond_init(&iothread->init_done_cond);
  86
  87     /* This assumes we are called from a thread with useful CPU affinity for us
  88      * to inherit.
  89      */
  90     qemu_thread_create(&iothread->thread, "iothread", iothread_run,
  91                        iothread, QEMU_THREAD_JOINABLE);
  92
  93     /* Wait for initialization to complete */
  94     qemu_mutex_lock(&iothread->init_done_lock);
  95     while (iothread->thread_id == -1) {
  96         qemu_cond_wait(&iothread->init_done_cond,
  97                        &iothread->init_done_lock);
  98     }
  99     qemu_mutex_unlock(&iothread->init_done_lock);
 100 }
 101
 102 static void iothread_class_init(ObjectClass *klass, void *class_data)
 103 {
 104     UserCreatableClass *ucc = USER_CREATABLE_CLASS(klass);
 105     ucc->complete = iothread_complete;
 106 }
 107
 108 static const TypeInfo iothread_info = {
 109     .name = TYPE_IOTHREAD,
 110     .parent = TYPE_OBJECT,
 111     .class_init = iothread_class_init,
 112     .instance_size = sizeof(IOThread),
 113     .instance_finalize = iothread_instance_finalize,
 114     .interfaces = (InterfaceInfo[]) {
 115         {TYPE_USER_CREATABLE},
 116         {}
 117     },
 118 };
 119
 120 static void iothread_register_types(void)
 121 {
 122     type_register_static(&iothread_info);
 123 }
 124
 125 type_init(iothread_register_types)
 126
 127 char *iothread_get_id(IOThread *iothread)
 128 {
 129     return object_get_canonical_path_component(OBJECT(iothread));
 130 }
 131
 132 AioContext *iothread_get_aio_context(IOThread *iothread)
 133 {
 134     return iothread->ctx;
 135 }
 136
 137 static int query_one_iothread(Object *object, void *opaque)
 138 {
 139     IOThreadInfoList ***prev = opaque;
 140     IOThreadInfoList *elem;
 141     IOThreadInfo *info;
 142     IOThread *iothread;
 143
 144     iothread = (IOThread *)object_dynamic_cast(object, TYPE_IOTHREAD);
 145     if (!iothread) {
 146         return 0;
 147     }
 148
 149     info = g_new0(IOThreadInfo, 1);
 150     info->id = iothread_get_id(iothread);
 151     info->thread_id = iothread->thread_id;
 152
 153     elem = g_new0(IOThreadInfoList, 1);
 154     elem->value = info;
 155     elem->next = NULL;
 156
 157     **prev = elem;
 158     *prev = &elem->next;
 159     return 0;
 160 }
 161
 162 IOThreadInfoList *qmp_query_iothreads(Error **errp)
 163 {
 164     IOThreadInfoList *head = NULL;
 165     IOThreadInfoList **prev = &head;
 166     Object *container = object_get_objects_root();
 167
 168     object_child_foreach(container, query_one_iothread, &prev);
 169     return head;
 170 }