qemu/aio-win32.c
Kevin Wolf 2ea9b58f0b aio: Fix return value of aio_poll()
aio_poll() must return true if any work is still pending, even if it
didn't make progress, so that bdrv_drain_all() doesn't stop waiting too
early. The possibility of stopping early occasionally lead to a failed
assertion in bdrv_drain_all(), when some in-flight request was missed
and the function didn't really drain all requests.

In order to make that change, the return value as specified in the
function comment must change for blocking = false; fortunately, the
return value of blocking = false callers is only used in test cases, so
this change shouldn't cause any trouble.

Cc: qemu-stable@nongnu.org
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-01-17 10:51:42 +01:00

220 lines
5.8 KiB
C

/*
* QEMU aio implementation
*
* Copyright IBM Corp., 2008
* Copyright Red Hat Inc., 2012
*
* Authors:
* Anthony Liguori <aliguori@us.ibm.com>
* Paolo Bonzini <pbonzini@redhat.com>
*
* This work is licensed under the terms of the GNU GPL, version 2. See
* the COPYING file in the top-level directory.
*
* Contributions after 2012-01-13 are licensed under the terms of the
* GNU GPL, version 2 or (at your option) any later version.
*/
#include "qemu-common.h"
#include "block/block.h"
#include "qemu/queue.h"
#include "qemu/sockets.h"
struct AioHandler {
EventNotifier *e;
EventNotifierHandler *io_notify;
AioFlushEventNotifierHandler *io_flush;
GPollFD pfd;
int deleted;
QLIST_ENTRY(AioHandler) node;
};
void aio_set_event_notifier(AioContext *ctx,
EventNotifier *e,
EventNotifierHandler *io_notify,
AioFlushEventNotifierHandler *io_flush)
{
AioHandler *node;
QLIST_FOREACH(node, &ctx->aio_handlers, node) {
if (node->e == e && !node->deleted) {
break;
}
}
/* Are we deleting the fd handler? */
if (!io_notify) {
if (node) {
g_source_remove_poll(&ctx->source, &node->pfd);
/* If the lock is held, just mark the node as deleted */
if (ctx->walking_handlers) {
node->deleted = 1;
node->pfd.revents = 0;
} else {
/* Otherwise, delete it for real. We can't just mark it as
* deleted because deleted nodes are only cleaned up after
* releasing the walking_handlers lock.
*/
QLIST_REMOVE(node, node);
g_free(node);
}
}
} else {
if (node == NULL) {
/* Alloc and insert if it's not already there */
node = g_malloc0(sizeof(AioHandler));
node->e = e;
node->pfd.fd = (uintptr_t)event_notifier_get_handle(e);
node->pfd.events = G_IO_IN;
QLIST_INSERT_HEAD(&ctx->aio_handlers, node, node);
g_source_add_poll(&ctx->source, &node->pfd);
}
/* Update handler with latest information */
node->io_notify = io_notify;
node->io_flush = io_flush;
}
aio_notify(ctx);
}
bool aio_pending(AioContext *ctx)
{
AioHandler *node;
QLIST_FOREACH(node, &ctx->aio_handlers, node) {
if (node->pfd.revents && node->io_notify) {
return true;
}
}
return false;
}
bool aio_poll(AioContext *ctx, bool blocking)
{
AioHandler *node;
HANDLE events[MAXIMUM_WAIT_OBJECTS + 1];
bool busy, progress;
int count;
progress = false;
/*
* If there are callbacks left that have been queued, we need to call then.
* Do not call select in this case, because it is possible that the caller
* does not need a complete flush (as is the case for qemu_aio_wait loops).
*/
if (aio_bh_poll(ctx)) {
blocking = false;
progress = true;
}
/*
* Then dispatch any pending callbacks from the GSource.
*
* We have to walk very carefully in case qemu_aio_set_fd_handler is
* called while we're walking.
*/
node = QLIST_FIRST(&ctx->aio_handlers);
while (node) {
AioHandler *tmp;
ctx->walking_handlers++;
if (node->pfd.revents && node->io_notify) {
node->pfd.revents = 0;
node->io_notify(node->e);
progress = true;
}
tmp = node;
node = QLIST_NEXT(node, node);
ctx->walking_handlers--;
if (!ctx->walking_handlers && tmp->deleted) {
QLIST_REMOVE(tmp, node);
g_free(tmp);
}
}
if (progress && !blocking) {
return true;
}
ctx->walking_handlers++;
/* fill fd sets */
busy = false;
count = 0;
QLIST_FOREACH(node, &ctx->aio_handlers, node) {
/* If there aren't pending AIO operations, don't invoke callbacks.
* Otherwise, if there are no AIO requests, qemu_aio_wait() would
* wait indefinitely.
*/
if (!node->deleted && node->io_flush) {
if (node->io_flush(node->e) == 0) {
continue;
}
busy = true;
}
if (!node->deleted && node->io_notify) {
events[count++] = event_notifier_get_handle(node->e);
}
}
ctx->walking_handlers--;
/* No AIO operations? Get us out of here */
if (!busy) {
return progress;
}
/* wait until next event */
while (count > 0) {
int timeout = blocking ? INFINITE : 0;
int ret = WaitForMultipleObjects(count, events, FALSE, timeout);
/* if we have any signaled events, dispatch event */
if ((DWORD) (ret - WAIT_OBJECT_0) >= count) {
break;
}
blocking = false;
/* we have to walk very carefully in case
* qemu_aio_set_fd_handler is called while we're walking */
node = QLIST_FIRST(&ctx->aio_handlers);
while (node) {
AioHandler *tmp;
ctx->walking_handlers++;
if (!node->deleted &&
event_notifier_get_handle(node->e) == events[ret - WAIT_OBJECT_0] &&
node->io_notify) {
node->io_notify(node->e);
progress = true;
}
tmp = node;
node = QLIST_NEXT(node, node);
ctx->walking_handlers--;
if (!ctx->walking_handlers && tmp->deleted) {
QLIST_REMOVE(tmp, node);
g_free(tmp);
}
}
/* Try again, but only call each handler once. */
events[ret - WAIT_OBJECT_0] = events[--count];
}
assert(progress || busy);
return true;
}