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/*
* QEMU aio implementation
*
* Copyright IBM, Corp. 2008
*
* Authors:
* Anthony Liguori <aliguori@us.ibm.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.h"
#include "qemu-queue.h"
#include "qemu_socket.h"
typedef struct AioHandler AioHandler;
/* The list of registered AIO handlers */
static QLIST_HEAD(, AioHandler) aio_handlers;
/* This is a simple lock used to protect the aio_handlers list. Specifically,
* it's used to ensure that no callbacks are removed while we're walking and
* dispatching callbacks.
*/
static int walking_handlers;
struct AioHandler
{
int fd;
IOHandler *io_read;
IOHandler *io_write;
AioFlushHandler *io_flush;
int deleted;
void *opaque;
QLIST_ENTRY(AioHandler) node;
};
static AioHandler *find_aio_handler(int fd)
{
AioHandler *node;
QLIST_FOREACH(node, &aio_handlers, node) {
if (node->fd == fd)
if (!node->deleted)
return node;
}
return NULL;
}
int qemu_aio_set_fd_handler(int fd,
IOHandler *io_read,
IOHandler *io_write,
AioFlushHandler *io_flush,
void *opaque)
{
AioHandler *node;
node = find_aio_handler(fd);
/* Are we deleting the fd handler? */
if (!io_read && !io_write) {
if (node) {
/* If the lock is held, just mark the node as deleted */
if (walking_handlers)
node->deleted = 1;
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->fd = fd;
QLIST_INSERT_HEAD(&aio_handlers, node, node);
}
/* Update handler with latest information */
node->io_read = io_read;
node->io_write = io_write;
node->io_flush = io_flush;
node->opaque = opaque;
}
qemu_set_fd_handler2(fd, NULL, io_read, io_write, opaque);
return 0;
}
void qemu_aio_flush(void)
{
while (qemu_aio_wait());
}
bool qemu_aio_wait(void)
{
AioHandler *node;
fd_set rdfds, wrfds;
int max_fd = -1;
int ret;
bool busy;
/*
* 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 (qemu_bh_poll()) {
return true;
}
walking_handlers++;
FD_ZERO(&rdfds);
FD_ZERO(&wrfds);
/* fill fd sets */
busy = false;
QLIST_FOREACH(node, &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->io_flush) {
if (node->io_flush(node->opaque) == 0) {
continue;
}
busy = true;
}
if (!node->deleted && node->io_read) {
FD_SET(node->fd, &rdfds);
max_fd = MAX(max_fd, node->fd + 1);
}
if (!node->deleted && node->io_write) {
FD_SET(node->fd, &wrfds);
max_fd = MAX(max_fd, node->fd + 1);
}
}
walking_handlers--;
/* No AIO operations? Get us out of here */
if (!busy) {
return false;
}
/* wait until next event */
ret = select(max_fd, &rdfds, &wrfds, NULL, NULL);
/* if we have any readable fds, dispatch event */
if (ret > 0) {
/* we have to walk very carefully in case
* qemu_aio_set_fd_handler is called while we're walking */
node = QLIST_FIRST(&aio_handlers);
while (node) {
AioHandler *tmp;
walking_handlers++;
if (!node->deleted &&
FD_ISSET(node->fd, &rdfds) &&
node->io_read) {
node->io_read(node->opaque);
}
if (!node->deleted &&
FD_ISSET(node->fd, &wrfds) &&
node->io_write) {
node->io_write(node->opaque);
}
tmp = node;
node = QLIST_NEXT(node, node);
walking_handlers--;
if (!walking_handlers && tmp->deleted) {
QLIST_REMOVE(tmp, node);
g_free(tmp);
}
}
}
return true;
}
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