/*
* QEMU System Emulator
*
* Copyright (c) 2003-2008 Fabrice Bellard
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
#include "qemu-common.h"
#include "block/aio.h"
#include "block/thread-pool.h"
#include "qemu/main-loop.h"
#include "qemu/atomic.h"
/***********************************************************/
/* bottom halves (can be seen as timers which expire ASAP) */
struct QEMUBH {
AioContext *ctx;
QEMUBHFunc *cb;
void *opaque;
QEMUBH *next;
bool scheduled;
bool idle;
bool deleted;
};
QEMUBH *aio_bh_new(AioContext *ctx, QEMUBHFunc *cb, void *opaque)
{
QEMUBH *bh;
bh = g_malloc0(sizeof(QEMUBH));
bh->ctx = ctx;
bh->cb = cb;
bh->opaque = opaque;
qemu_mutex_lock(&ctx->bh_lock);
bh->next = ctx->first_bh;
/* Make sure that the members are ready before putting bh into list */
smp_wmb();
ctx->first_bh = bh;
qemu_mutex_unlock(&ctx->bh_lock);
return bh;
}
/* Multiple occurrences of aio_bh_poll cannot be called concurrently */
int aio_bh_poll(AioContext *ctx)
{
QEMUBH *bh, **bhp, *next;
int ret;
ctx->walking_bh++;
ret = 0;
for (bh = ctx->first_bh; bh; bh = next) {
/* Make sure that fetching bh happens before accessing its members */
smp_read_barrier_depends();
next = bh->next;
if (!bh->deleted && bh->scheduled) {
bh->scheduled = 0;
/* Paired with write barrier in bh schedule to ensure reading for
* idle & callbacks coming after bh's scheduling.
*/
smp_rmb();
if (!bh->idle)
ret = 1;
bh->idle = 0;
bh->cb(bh->opaque);
}
}
ctx->walking_bh--;
/* remove deleted bhs */
if (!ctx->walking_bh) {
qemu_mutex_lock(&ctx->bh_lock);
bhp = &ctx->first_bh;
while (*bhp) {
bh = *bhp;
if (bh->deleted) {
*bhp = bh->next;
g_free(bh);
} else {
bhp = &bh->next;
}
}
qemu_mutex_unlock(&ctx->bh_lock);
}
return ret;
}
void qemu_bh_schedule_idle(QEMUBH *bh)
{
if (bh->scheduled)
return;
bh->idle = 1;
/* Make sure that idle & any writes needed by the callback are done
* before the locations are read in the aio_bh_poll.
*/
smp_wmb();
bh->scheduled = 1;
}
void qemu_bh_schedule(QEMUBH *bh)
{
AioContext *ctx;
if (bh->scheduled)
return;
ctx = bh->ctx;
bh->idle = 0;
/* Make sure that:
* 1. idle & any writes needed by the callback are done before the
* locations are read in the aio_bh_poll.
* 2. ctx is loaded before scheduled is set and the callback has a chance
* to execute.
*/
smp_mb();
bh->scheduled = 1;
aio_notify(ctx);
}
/* This func is async.
*/
void qemu_bh_cancel(QEMUBH *bh)
{
bh->scheduled = 0;
}
/* This func is async.The bottom half will do the delete action at the finial
* end.
*/
void qemu_bh_delete(QEMUBH *bh)
{
bh->scheduled = 0;
bh->deleted = 1;
}
int64_t
aio_compute_timeout(AioContext *ctx)
{
int64_t deadline;
int timeout = -1;
QEMUBH *bh;
for (bh = ctx->first_bh; bh; bh = bh->next) {
if (!bh->deleted && bh->scheduled) {
if (bh->idle) {
/* idle bottom halves will be polled at least
* every 10ms */
timeout = 10000000;
} else {
/* non-idle bottom halves will be executed
* immediately */
return 0;
}
}
}
deadline = timerlistgroup_deadline_ns(&ctx->tlg);
if (deadline == 0) {
return 0;
} else {
return qemu_soonest_timeout(timeout, deadline);
}
}
static gboolean
aio_ctx_prepare(GSource *source, gint *timeout)
{
AioContext *ctx = (AioContext *) source;
/* We assume there is no timeout already supplied */
*timeout = qemu_timeout_ns_to_ms(aio_compute_timeout(ctx));
return *timeout == 0;
}
static gboolean
aio_ctx_check(GSource *source)
{
AioContext *ctx = (AioContext *) source;
QEMUBH *bh;
for (bh = ctx->first_bh; bh; bh = bh->next) {
if (!bh->deleted && bh->scheduled) {
return true;
}
}
return aio_pending(ctx) || (timerlistgroup_deadline_ns(&ctx->tlg) == 0);
}
static gboolean
aio_ctx_dispatch(GSource *source,
GSourceFunc callback,
gpointer user_data)
{
AioContext *ctx = (AioContext *) source;
assert(callback == NULL);
aio_poll(ctx, false);
return true;
}
static void
aio_ctx_finalize(GSource *source)
{
AioContext *ctx = (AioContext *) source;
thread_pool_free(ctx->thread_pool);
aio_set_event_notifier(ctx, &ctx->notifier, NULL);
event_notifier_cleanup(&ctx->notifier);
rfifolock_destroy(&ctx->lock);
qemu_mutex_destroy(&ctx->bh_lock);
g_array_free(ctx->pollfds, TRUE);
timerlistgroup_deinit(&ctx->tlg);
}
static GSourceFuncs aio_source_funcs = {
aio_ctx_prepare,
aio_ctx_check,
aio_ctx_dispatch,
aio_ctx_finalize
};
GSource *aio_get_g_source(AioContext *ctx)
{
g_source_ref(&ctx->source);
return &ctx->source;
}
ThreadPool *aio_get_thread_pool(AioContext *ctx)
{
if (!ctx->thread_pool) {
ctx->thread_pool = thread_pool_new(ctx);
}
return ctx->thread_pool;
}
void aio_set_dispatching(AioContext *ctx, bool dispatching)
{
ctx->dispatching = dispatching;
if (!dispatching) {
/* Write ctx->dispatching before reading e.g. bh->scheduled.
* Optimization: this is only needed when we're entering the "unsafe"
* phase where other threads must call event_notifier_set.
*/
smp_mb();
}
}
void aio_notify(AioContext *ctx)
{
/* Write e.g. bh->scheduled before reading ctx->dispatching. */
smp_mb();
if (!ctx->dispatching) {
event_notifier_set(&ctx->notifier);
}
}
static void aio_timerlist_notify(void *opaque)
{
aio_notify(opaque);
}
static void aio_rfifolock_cb(void *opaque)
{
/* Kick owner thread in case they are blocked in aio_poll() */
aio_notify(opaque);
}
AioContext *aio_context_new(void)
{
AioContext *ctx;
ctx = (AioContext *) g_source_new(&aio_source_funcs, sizeof(AioContext));
ctx->pollfds = g_array_new(FALSE, FALSE, sizeof(GPollFD));
ctx->thread_pool = NULL;
qemu_mutex_init(&ctx->bh_lock);
rfifolock_init(&ctx->lock, aio_rfifolock_cb, ctx);
event_notifier_init(&ctx->notifier, false);
aio_set_event_notifier(ctx, &ctx->notifier,
(EventNotifierHandler *)
event_notifier_test_and_clear);
timerlistgroup_init(&ctx->tlg, aio_timerlist_notify, ctx);
return ctx;
}
void aio_context_ref(AioContext *ctx)
{
g_source_ref(&ctx->source);
}
void aio_context_unref(AioContext *ctx)
{
g_source_unref(&ctx->source);
}
void aio_context_acquire(AioContext *ctx)
{
rfifolock_lock(&ctx->lock);
}
void aio_context_release(AioContext *ctx)
{
rfifolock_unlock(&ctx->lock);
}
