/*
* 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/block.h"
#include "qemu/queue.h"
#include "qemu/sockets.h"
struct AioHandler
{
GPollFD pfd;
IOHandler *io_read;
IOHandler *io_write;
int deleted;
int pollfds_idx;
void *opaque;
QLIST_ENTRY(AioHandler) node;
};
static AioHandler *find_aio_handler(AioContext *ctx, int fd)
{
AioHandler *node;
QLIST_FOREACH(node, &ctx->aio_handlers, node) {
if (node->pfd.fd == fd)
if (!node->deleted)
return node;
}
return NULL;
}
void aio_set_fd_handler(AioContext *ctx,
int fd,
IOHandler *io_read,
IOHandler *io_write,
void *opaque)
{
AioHandler *node;
node = find_aio_handler(ctx, fd);
/* Are we deleting the fd handler? */
if (!io_read && !io_write) {
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->pfd.fd = fd;
QLIST_INSERT_HEAD(&ctx->aio_handlers, node, node);
g_source_add_poll(&ctx->source, &node->pfd);
}
/* Update handler with latest information */
node->io_read = io_read;
node->io_write = io_write;
node->opaque = opaque;
node->pollfds_idx = -1;
node->pfd.events = (io_read ? G_IO_IN | G_IO_HUP | G_IO_ERR : 0);
node->pfd.events |= (io_write ? G_IO_OUT | G_IO_ERR : 0);
}
aio_notify(ctx);
}
void aio_set_event_notifier(AioContext *ctx,
EventNotifier *notifier,
EventNotifierHandler *io_read)
{
aio_set_fd_handler(ctx, event_notifier_get_fd(notifier),
(IOHandler *)io_read, NULL, notifier);
}
bool aio_pending(AioContext *ctx)
{
AioHandler *node;
QLIST_FOREACH(node, &ctx->aio_handlers, node) {
int revents;
revents = node->pfd.revents & node->pfd.events;
if (revents & (G_IO_IN | G_IO_HUP | G_IO_ERR) && node->io_read) {
return true;
}
if (revents & (G_IO_OUT | G_IO_ERR) && node->io_write) {
return true;
}
}
return false;
}
static bool aio_dispatch(AioContext *ctx)
{
AioHandler *node;
bool progress = false;
/*
* We have to walk very carefully in case aio_set_fd_handler is
* called while we're walking.
*/
node = QLIST_FIRST(&ctx->aio_handlers);
while (node) {
AioHandler *tmp;
int revents;
ctx->walking_handlers++;
revents = node->pfd.revents & node->pfd.events;
node->pfd.revents = 0;
if (!node->deleted &&
(revents & (G_IO_IN | G_IO_HUP | G_IO_ERR)) &&
node->io_read) {
node->io_read(node->opaque);
/* aio_notify() does not count as progress */
if (node->opaque != &ctx->notifier) {
progress = true;
}
}
if (!node->deleted &&
(revents & (G_IO_OUT | G_IO_ERR)) &&
node->io_write) {
node->io_write(node->opaque);
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);
}
}
/* Run our timers */
progress |= timerlistgroup_run_timers(&ctx->tlg);
return progress;
}
bool aio_poll(AioContext *ctx, bool blocking)
{
AioHandler *node;
bool was_dispatching;
int ret;
bool progress;
was_dispatching = ctx->dispatching;
progress = false;
/* aio_notify can avoid the expensive event_notifier_set if
* everything (file descriptors, bottom halves, timers) will
* be re-evaluated before the next blocking poll(). This happens
* in two cases:
*
* 1) when aio_poll is called with blocking == false
*
* 2) when we are called after poll(). If we are called before
* poll(), bottom halves will not be re-evaluated and we need
* aio_notify() if blocking == true.
*
* The first aio_dispatch() only does something when AioContext is
* running as a GSource, and in that case aio_poll is used only
* with blocking == false, so this optimization is already quite
* effective. However, the code is ugly and should be restructured
* to have a single aio_dispatch() call. To do this, we need to
* reorganize aio_poll into a prepare/poll/dispatch model like
* glib's.
*
* If we're in a nested event loop, ctx->dispatching might be true.
* In that case we can restore it just before returning, but we
* have to clear it now.
*/
aio_set_dispatching(ctx, !blocking);
/*
* If there are callbacks left that have been queued, we need to call them.
* 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 aio_poll loops).
*/
if (aio_bh_poll(ctx)) {
blocking = false;
progress = true;
}
/* Re-evaluate condition (1) above. */
aio_set_dispatching(ctx, !blocking);
if (aio_dispatch(ctx)) {
progress = true;
}
if (progress && !blocking) {
goto out;
}
ctx->walking_handlers++;
g_array_set_size(ctx->pollfds, 0);
/* fill pollfds */
QLIST_FOREACH(node, &ctx->aio_handlers, node) {
node->pollfds_idx = -1;
if (!node->deleted && node->pfd.events) {
GPollFD pfd = {
.fd = node->pfd.fd,
.events = node->pfd.events,
};
node->pollfds_idx = ctx->pollfds->len;
g_array_append_val(ctx->pollfds, pfd);
}
}
ctx->walking_handlers--;
/* wait until next event */
ret = qemu_poll_ns((GPollFD *)ctx->pollfds->data,
ctx->pollfds->len,
blocking ? timerlistgroup_deadline_ns(&ctx->tlg) : 0);
/* if we have any readable fds, dispatch event */
if (ret > 0) {
QLIST_FOREACH(node, &ctx->aio_handlers, node) {
if (node->pollfds_idx != -1) {
GPollFD *pfd = &g_array_index(ctx->pollfds, GPollFD,
node->pollfds_idx);
node->pfd.revents = pfd->revents;
}
}
}
/* Run dispatch even if there were no readable fds to run timers */
aio_set_dispatching(ctx, true);
if (aio_dispatch(ctx)) {
progress = true;
}
out:
aio_set_dispatching(ctx, was_dispatching);
return progress;
}
