qemu-e2k/util/async.c

509 lines
13 KiB
C

/*
* Data plane event loop
*
* Copyright (c) 2003-2008 Fabrice Bellard
* Copyright (c) 2009-2017 QEMU contributors
*
* 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/osdep.h"
#include "qapi/error.h"
#include "qemu-common.h"
#include "block/aio.h"
#include "block/thread-pool.h"
#include "qemu/main-loop.h"
#include "qemu/atomic.h"
#include "block/raw-aio.h"
#include "qemu/coroutine_int.h"
#include "trace.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;
};
void aio_bh_schedule_oneshot(AioContext *ctx, QEMUBHFunc *cb, void *opaque)
{
QEMUBH *bh;
bh = g_new(QEMUBH, 1);
*bh = (QEMUBH){
.ctx = ctx,
.cb = cb,
.opaque = opaque,
};
qemu_lockcnt_lock(&ctx->list_lock);
bh->next = ctx->first_bh;
bh->scheduled = 1;
bh->deleted = 1;
/* Make sure that the members are ready before putting bh into list */
smp_wmb();
ctx->first_bh = bh;
qemu_lockcnt_unlock(&ctx->list_lock);
aio_notify(ctx);
}
QEMUBH *aio_bh_new(AioContext *ctx, QEMUBHFunc *cb, void *opaque)
{
QEMUBH *bh;
bh = g_new(QEMUBH, 1);
*bh = (QEMUBH){
.ctx = ctx,
.cb = cb,
.opaque = opaque,
};
qemu_lockcnt_lock(&ctx->list_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_lockcnt_unlock(&ctx->list_lock);
return bh;
}
void aio_bh_call(QEMUBH *bh)
{
bh->cb(bh->opaque);
}
/* Multiple occurrences of aio_bh_poll cannot be called concurrently.
* The count in ctx->list_lock is incremented before the call, and is
* not affected by the call.
*/
int aio_bh_poll(AioContext *ctx)
{
QEMUBH *bh, **bhp, *next;
int ret;
bool deleted = false;
ret = 0;
for (bh = atomic_rcu_read(&ctx->first_bh); bh; bh = next) {
next = atomic_rcu_read(&bh->next);
/* The atomic_xchg is paired with the one in qemu_bh_schedule. The
* implicit memory barrier ensures that the callback sees all writes
* done by the scheduling thread. It also ensures that the scheduling
* thread sees the zero before bh->cb has run, and thus will call
* aio_notify again if necessary.
*/
if (atomic_xchg(&bh->scheduled, 0)) {
/* Idle BHs don't count as progress */
if (!bh->idle) {
ret = 1;
}
bh->idle = 0;
aio_bh_call(bh);
}
if (bh->deleted) {
deleted = true;
}
}
/* remove deleted bhs */
if (!deleted) {
return ret;
}
if (qemu_lockcnt_dec_if_lock(&ctx->list_lock)) {
bhp = &ctx->first_bh;
while (*bhp) {
bh = *bhp;
if (bh->deleted && !bh->scheduled) {
*bhp = bh->next;
g_free(bh);
} else {
bhp = &bh->next;
}
}
qemu_lockcnt_inc_and_unlock(&ctx->list_lock);
}
return ret;
}
void qemu_bh_schedule_idle(QEMUBH *bh)
{
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.
*/
atomic_mb_set(&bh->scheduled, 1);
}
void qemu_bh_schedule(QEMUBH *bh)
{
AioContext *ctx;
ctx = bh->ctx;
bh->idle = 0;
/* The memory barrier implicit in atomic_xchg makes 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.
*/
if (atomic_xchg(&bh->scheduled, 1) == 0) {
aio_notify(ctx);
}
}
/* This func is async.
*/
void qemu_bh_cancel(QEMUBH *bh)
{
atomic_mb_set(&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 = atomic_rcu_read(&ctx->first_bh); bh;
bh = atomic_rcu_read(&bh->next)) {
if (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;
atomic_or(&ctx->notify_me, 1);
/* We assume there is no timeout already supplied */
*timeout = qemu_timeout_ns_to_ms(aio_compute_timeout(ctx));
if (aio_prepare(ctx)) {
*timeout = 0;
}
return *timeout == 0;
}
static gboolean
aio_ctx_check(GSource *source)
{
AioContext *ctx = (AioContext *) source;
QEMUBH *bh;
atomic_and(&ctx->notify_me, ~1);
aio_notify_accept(ctx);
for (bh = ctx->first_bh; bh; bh = bh->next) {
if (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_dispatch(ctx);
return true;
}
static void
aio_ctx_finalize(GSource *source)
{
AioContext *ctx = (AioContext *) source;
thread_pool_free(ctx->thread_pool);
#ifdef CONFIG_LINUX_AIO
if (ctx->linux_aio) {
laio_detach_aio_context(ctx->linux_aio, ctx);
laio_cleanup(ctx->linux_aio);
ctx->linux_aio = NULL;
}
#endif
assert(QSLIST_EMPTY(&ctx->scheduled_coroutines));
qemu_bh_delete(ctx->co_schedule_bh);
qemu_lockcnt_lock(&ctx->list_lock);
assert(!qemu_lockcnt_count(&ctx->list_lock));
while (ctx->first_bh) {
QEMUBH *next = ctx->first_bh->next;
/* qemu_bh_delete() must have been called on BHs in this AioContext */
assert(ctx->first_bh->deleted);
g_free(ctx->first_bh);
ctx->first_bh = next;
}
qemu_lockcnt_unlock(&ctx->list_lock);
aio_set_event_notifier(ctx, &ctx->notifier, false, NULL, NULL);
event_notifier_cleanup(&ctx->notifier);
qemu_rec_mutex_destroy(&ctx->lock);
qemu_lockcnt_destroy(&ctx->list_lock);
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;
}
#ifdef CONFIG_LINUX_AIO
LinuxAioState *aio_get_linux_aio(AioContext *ctx)
{
if (!ctx->linux_aio) {
ctx->linux_aio = laio_init();
laio_attach_aio_context(ctx->linux_aio, ctx);
}
return ctx->linux_aio;
}
#endif
void aio_notify(AioContext *ctx)
{
/* Write e.g. bh->scheduled before reading ctx->notify_me. Pairs
* with atomic_or in aio_ctx_prepare or atomic_add in aio_poll.
*/
smp_mb();
if (ctx->notify_me) {
event_notifier_set(&ctx->notifier);
atomic_mb_set(&ctx->notified, true);
}
}
void aio_notify_accept(AioContext *ctx)
{
if (atomic_xchg(&ctx->notified, false)) {
event_notifier_test_and_clear(&ctx->notifier);
}
}
static void aio_timerlist_notify(void *opaque, QEMUClockType type)
{
aio_notify(opaque);
}
static void event_notifier_dummy_cb(EventNotifier *e)
{
}
/* Returns true if aio_notify() was called (e.g. a BH was scheduled) */
static bool event_notifier_poll(void *opaque)
{
EventNotifier *e = opaque;
AioContext *ctx = container_of(e, AioContext, notifier);
return atomic_read(&ctx->notified);
}
static void co_schedule_bh_cb(void *opaque)
{
AioContext *ctx = opaque;
QSLIST_HEAD(, Coroutine) straight, reversed;
QSLIST_MOVE_ATOMIC(&reversed, &ctx->scheduled_coroutines);
QSLIST_INIT(&straight);
while (!QSLIST_EMPTY(&reversed)) {
Coroutine *co = QSLIST_FIRST(&reversed);
QSLIST_REMOVE_HEAD(&reversed, co_scheduled_next);
QSLIST_INSERT_HEAD(&straight, co, co_scheduled_next);
}
while (!QSLIST_EMPTY(&straight)) {
Coroutine *co = QSLIST_FIRST(&straight);
QSLIST_REMOVE_HEAD(&straight, co_scheduled_next);
trace_aio_co_schedule_bh_cb(ctx, co);
aio_context_acquire(ctx);
/* Protected by write barrier in qemu_aio_coroutine_enter */
atomic_set(&co->scheduled, NULL);
qemu_coroutine_enter(co);
aio_context_release(ctx);
}
}
AioContext *aio_context_new(Error **errp)
{
int ret;
AioContext *ctx;
ctx = (AioContext *) g_source_new(&aio_source_funcs, sizeof(AioContext));
aio_context_setup(ctx);
ret = event_notifier_init(&ctx->notifier, false);
if (ret < 0) {
error_setg_errno(errp, -ret, "Failed to initialize event notifier");
goto fail;
}
g_source_set_can_recurse(&ctx->source, true);
qemu_lockcnt_init(&ctx->list_lock);
ctx->co_schedule_bh = aio_bh_new(ctx, co_schedule_bh_cb, ctx);
QSLIST_INIT(&ctx->scheduled_coroutines);
aio_set_event_notifier(ctx, &ctx->notifier,
false,
(EventNotifierHandler *)
event_notifier_dummy_cb,
event_notifier_poll);
#ifdef CONFIG_LINUX_AIO
ctx->linux_aio = NULL;
#endif
ctx->thread_pool = NULL;
qemu_rec_mutex_init(&ctx->lock);
timerlistgroup_init(&ctx->tlg, aio_timerlist_notify, ctx);
ctx->poll_ns = 0;
ctx->poll_max_ns = 0;
ctx->poll_grow = 0;
ctx->poll_shrink = 0;
return ctx;
fail:
g_source_destroy(&ctx->source);
return NULL;
}
void aio_co_schedule(AioContext *ctx, Coroutine *co)
{
trace_aio_co_schedule(ctx, co);
const char *scheduled = atomic_cmpxchg(&co->scheduled, NULL,
__func__);
if (scheduled) {
fprintf(stderr,
"%s: Co-routine was already scheduled in '%s'\n",
__func__, scheduled);
abort();
}
QSLIST_INSERT_HEAD_ATOMIC(&ctx->scheduled_coroutines,
co, co_scheduled_next);
qemu_bh_schedule(ctx->co_schedule_bh);
}
void aio_co_wake(struct Coroutine *co)
{
AioContext *ctx;
/* Read coroutine before co->ctx. Matches smp_wmb in
* qemu_coroutine_enter.
*/
smp_read_barrier_depends();
ctx = atomic_read(&co->ctx);
aio_co_enter(ctx, co);
}
void aio_co_enter(AioContext *ctx, struct Coroutine *co)
{
if (ctx != qemu_get_current_aio_context()) {
aio_co_schedule(ctx, co);
return;
}
if (qemu_in_coroutine()) {
Coroutine *self = qemu_coroutine_self();
assert(self != co);
QSIMPLEQ_INSERT_TAIL(&self->co_queue_wakeup, co, co_queue_next);
} else {
aio_context_acquire(ctx);
qemu_aio_coroutine_enter(ctx, co);
aio_context_release(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)
{
qemu_rec_mutex_lock(&ctx->lock);
}
void aio_context_release(AioContext *ctx)
{
qemu_rec_mutex_unlock(&ctx->lock);
}