qemu/iothread.c
Chrysostomos Nanakos 2f78e491d7 async: aio_context_new(): Handle event_notifier_init failure
On a system with a low limit of open files the initialization
of the event notifier could fail and QEMU exits without printing any
error information to the user.

The problem can be easily reproduced by enforcing a low limit of open
files and start QEMU with enough I/O threads to hit this limit.

The same problem raises, without the creation of I/O threads, while
QEMU initializes the main event loop by enforcing an even lower limit of
open files.

This commit adds an error message on failure:

 # qemu [...] -object iothread,id=iothread0 -object iothread,id=iothread1
 qemu: Failed to initialize event notifier: Too many open files in system

Signed-off-by: Chrysostomos Nanakos <cnanakos@grnet.gr>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2014-09-22 11:39:48 +01:00

180 lines
4.5 KiB
C

/*
* Event loop thread
*
* Copyright Red Hat Inc., 2013
*
* Authors:
* Stefan Hajnoczi <stefanha@redhat.com>
*
* This work is licensed under the terms of the GNU GPL, version 2 or later.
* See the COPYING file in the top-level directory.
*
*/
#include "qom/object.h"
#include "qom/object_interfaces.h"
#include "qemu/module.h"
#include "block/aio.h"
#include "sysemu/iothread.h"
#include "qmp-commands.h"
#include "qemu/error-report.h"
#define IOTHREADS_PATH "/objects"
typedef ObjectClass IOThreadClass;
#define IOTHREAD_GET_CLASS(obj) \
OBJECT_GET_CLASS(IOThreadClass, obj, TYPE_IOTHREAD)
#define IOTHREAD_CLASS(klass) \
OBJECT_CLASS_CHECK(IOThreadClass, klass, TYPE_IOTHREAD)
static void *iothread_run(void *opaque)
{
IOThread *iothread = opaque;
bool blocking;
qemu_mutex_lock(&iothread->init_done_lock);
iothread->thread_id = qemu_get_thread_id();
qemu_cond_signal(&iothread->init_done_cond);
qemu_mutex_unlock(&iothread->init_done_lock);
while (!iothread->stopping) {
aio_context_acquire(iothread->ctx);
blocking = true;
while (!iothread->stopping && aio_poll(iothread->ctx, blocking)) {
/* Progress was made, keep going */
blocking = false;
}
aio_context_release(iothread->ctx);
}
return NULL;
}
static void iothread_instance_finalize(Object *obj)
{
IOThread *iothread = IOTHREAD(obj);
if (!iothread->ctx) {
return;
}
iothread->stopping = true;
aio_notify(iothread->ctx);
qemu_thread_join(&iothread->thread);
qemu_cond_destroy(&iothread->init_done_cond);
qemu_mutex_destroy(&iothread->init_done_lock);
aio_context_unref(iothread->ctx);
}
static void iothread_complete(UserCreatable *obj, Error **errp)
{
Error *local_error = NULL;
IOThread *iothread = IOTHREAD(obj);
iothread->stopping = false;
iothread->thread_id = -1;
iothread->ctx = aio_context_new(&local_error);
if (!iothread->ctx) {
error_propagate(errp, local_error);
return;
}
qemu_mutex_init(&iothread->init_done_lock);
qemu_cond_init(&iothread->init_done_cond);
/* This assumes we are called from a thread with useful CPU affinity for us
* to inherit.
*/
qemu_thread_create(&iothread->thread, "iothread", iothread_run,
iothread, QEMU_THREAD_JOINABLE);
/* Wait for initialization to complete */
qemu_mutex_lock(&iothread->init_done_lock);
while (iothread->thread_id == -1) {
qemu_cond_wait(&iothread->init_done_cond,
&iothread->init_done_lock);
}
qemu_mutex_unlock(&iothread->init_done_lock);
}
static void iothread_class_init(ObjectClass *klass, void *class_data)
{
UserCreatableClass *ucc = USER_CREATABLE_CLASS(klass);
ucc->complete = iothread_complete;
}
static const TypeInfo iothread_info = {
.name = TYPE_IOTHREAD,
.parent = TYPE_OBJECT,
.class_init = iothread_class_init,
.instance_size = sizeof(IOThread),
.instance_finalize = iothread_instance_finalize,
.interfaces = (InterfaceInfo[]) {
{TYPE_USER_CREATABLE},
{}
},
};
static void iothread_register_types(void)
{
type_register_static(&iothread_info);
}
type_init(iothread_register_types)
IOThread *iothread_find(const char *id)
{
Object *container = container_get(object_get_root(), IOTHREADS_PATH);
Object *child;
child = object_property_get_link(container, id, NULL);
if (!child) {
return NULL;
}
return (IOThread *)object_dynamic_cast(child, TYPE_IOTHREAD);
}
char *iothread_get_id(IOThread *iothread)
{
return object_get_canonical_path_component(OBJECT(iothread));
}
AioContext *iothread_get_aio_context(IOThread *iothread)
{
return iothread->ctx;
}
static int query_one_iothread(Object *object, void *opaque)
{
IOThreadInfoList ***prev = opaque;
IOThreadInfoList *elem;
IOThreadInfo *info;
IOThread *iothread;
iothread = (IOThread *)object_dynamic_cast(object, TYPE_IOTHREAD);
if (!iothread) {
return 0;
}
info = g_new0(IOThreadInfo, 1);
info->id = iothread_get_id(iothread);
info->thread_id = iothread->thread_id;
elem = g_new0(IOThreadInfoList, 1);
elem->value = info;
elem->next = NULL;
**prev = elem;
*prev = &elem->next;
return 0;
}
IOThreadInfoList *qmp_query_iothreads(Error **errp)
{
IOThreadInfoList *head = NULL;
IOThreadInfoList **prev = &head;
Object *container = container_get(object_get_root(), IOTHREADS_PATH);
object_child_foreach(container, query_one_iothread, &prev);
return head;
}