/*
* 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 "block/aio.h"
#include "block/thread-pool.h"
#include "qemu/main-loop.h"
#include "qemu/atomic.h"
#include "qemu/rcu_queue.h"
#include "block/raw-aio.h"
#include "qemu/coroutine_int.h"
#include "trace.h"
/***********************************************************/
/* bottom halves (can be seen as timers which expire ASAP) */
/* QEMUBH::flags values */
enum {
/* Already enqueued and waiting for aio_bh_poll() */
BH_PENDING = (1 << 0),
/* Invoke the callback */
BH_SCHEDULED = (1 << 1),
/* Delete without invoking callback */
BH_DELETED = (1 << 2),
/* Delete after invoking callback */
BH_ONESHOT = (1 << 3),
/* Schedule periodically when the event loop is idle */
BH_IDLE = (1 << 4),
};
struct QEMUBH {
AioContext *ctx;
QEMUBHFunc *cb;
void *opaque;
QSLIST_ENTRY(QEMUBH) next;
unsigned flags;
};
/* Called concurrently from any thread */
static void aio_bh_enqueue(QEMUBH *bh, unsigned new_flags)
{
AioContext *ctx = bh->ctx;
unsigned old_flags;
/*
* The memory barrier implicit in qatomic_fetch_or 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 the callback has a chance to execute and bh
* could be freed.
*/
old_flags = qatomic_fetch_or(&bh->flags, BH_PENDING | new_flags);
if (!(old_flags & BH_PENDING)) {
QSLIST_INSERT_HEAD_ATOMIC(&ctx->bh_list, bh, next);
}
aio_notify(ctx);
}
/* Only called from aio_bh_poll() and aio_ctx_finalize() */
static QEMUBH *aio_bh_dequeue(BHList *head, unsigned *flags)
{
QEMUBH *bh = QSLIST_FIRST_RCU(head);
if (!bh) {
return NULL;
}
QSLIST_REMOVE_HEAD(head, next);
/*
* The qatomic_and is paired with aio_bh_enqueue(). 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 cleared
* flag before bh->cb has run, and thus will call aio_notify again if
* necessary.
*/
*flags = qatomic_fetch_and(&bh->flags,
~(BH_PENDING | BH_SCHEDULED | BH_IDLE));
return bh;
}
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,
};
aio_bh_enqueue(bh, BH_SCHEDULED | BH_ONESHOT);
}
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,
};
return bh;
}
void aio_bh_call(QEMUBH *bh)
{
bh->cb(bh->opaque);
}
/* Multiple occurrences of aio_bh_poll cannot be called concurrently. */
int aio_bh_poll(AioContext *ctx)
{
BHListSlice slice;
BHListSlice *s;
int ret = 0;
QSLIST_MOVE_ATOMIC(&slice.bh_list, &ctx->bh_list);
QSIMPLEQ_INSERT_TAIL(&ctx->bh_slice_list, &slice, next);
while ((s = QSIMPLEQ_FIRST(&ctx->bh_slice_list))) {
QEMUBH *bh;
unsigned flags;
bh = aio_bh_dequeue(&s->bh_list, &flags);
if (!bh) {
QSIMPLEQ_REMOVE_HEAD(&ctx->bh_slice_list, next);
continue;
}
if ((flags & (BH_SCHEDULED | BH_DELETED)) == BH_SCHEDULED) {
/* Idle BHs don't count as progress */
if (!(flags & BH_IDLE)) {
ret = 1;
}
aio_bh_call(bh);
}
if (flags & (BH_DELETED | BH_ONESHOT)) {
g_free(bh);
}
}
return ret;
}
void qemu_bh_schedule_idle(QEMUBH *bh)
{
aio_bh_enqueue(bh, BH_SCHEDULED | BH_IDLE);
}
void qemu_bh_schedule(QEMUBH *bh)
{
aio_bh_enqueue(bh, BH_SCHEDULED);
}
/* This func is async.
*/
void qemu_bh_cancel(QEMUBH *bh)
{
qatomic_and(&bh->flags, ~BH_SCHEDULED);
}
/* This func is async.The bottom half will do the delete action at the finial
* end.
*/
void qemu_bh_delete(QEMUBH *bh)
{
aio_bh_enqueue(bh, BH_DELETED);
}
static int64_t aio_compute_bh_timeout(BHList *head, int timeout)
{
QEMUBH *bh;
QSLIST_FOREACH_RCU(bh, head, next) {
if ((bh->flags & (BH_SCHEDULED | BH_DELETED)) == BH_SCHEDULED) {
if (bh->flags & 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;
}
}
}
return timeout;
}
int64_t
aio_compute_timeout(AioContext *ctx)
{
BHListSlice *s;
int64_t deadline;
int timeout = -1;
timeout = aio_compute_bh_timeout(&ctx->bh_list, timeout);
if (timeout == 0) {
return 0;
}
QSIMPLEQ_FOREACH(s, &ctx->bh_slice_list, next) {
timeout = aio_compute_bh_timeout(&s->bh_list, timeout);
if (timeout == 0) {
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;
qatomic_set(&ctx->notify_me, qatomic_read(&ctx->notify_me) | 1);
/*
* Write ctx->notify_me before computing the timeout
* (reading bottom half flags, etc.). Pairs with
* smp_mb in aio_notify().
*/
smp_mb();
/* 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;
BHListSlice *s;
/* Finish computing the timeout before clearing the flag. */
qatomic_store_release(&ctx->notify_me, qatomic_read(&ctx->notify_me) & ~1);
aio_notify_accept(ctx);
QSLIST_FOREACH_RCU(bh, &ctx->bh_list, next) {
if ((bh->flags & (BH_SCHEDULED | BH_DELETED)) == BH_SCHEDULED) {
return true;
}
}
QSIMPLEQ_FOREACH(s, &ctx->bh_slice_list, next) {
QSLIST_FOREACH_RCU(bh, &s->bh_list, next) {
if ((bh->flags & (BH_SCHEDULED | 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_dispatch(ctx);
return true;
}
static void
aio_ctx_finalize(GSource *source)
{
AioContext *ctx = (AioContext *) source;
QEMUBH *bh;
unsigned flags;
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
#ifdef CONFIG_LINUX_IO_URING
if (ctx->linux_io_uring) {
luring_detach_aio_context(ctx->linux_io_uring, ctx);
luring_cleanup(ctx->linux_io_uring);
ctx->linux_io_uring = NULL;
}
#endif
assert(QSLIST_EMPTY(&ctx->scheduled_coroutines));
qemu_bh_delete(ctx->co_schedule_bh);
/* There must be no aio_bh_poll() calls going on */
assert(QSIMPLEQ_EMPTY(&ctx->bh_slice_list));
while ((bh = aio_bh_dequeue(&ctx->bh_list, &flags))) {
/* qemu_bh_delete() must have been called on BHs in this AioContext */
assert(flags & BH_DELETED);
g_free(bh);
}
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);
aio_context_destroy(ctx);
}
static GSourceFuncs aio_source_funcs = {
aio_ctx_prepare,
aio_ctx_check,
aio_ctx_dispatch,
aio_ctx_finalize
};
GSource *aio_get_g_source(AioContext *ctx)
{
aio_context_use_g_source(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_setup_linux_aio(AioContext *ctx, Error **errp)
{
if (!ctx->linux_aio) {
ctx->linux_aio = laio_init(errp);
if (ctx->linux_aio) {
laio_attach_aio_context(ctx->linux_aio, ctx);
}
}
return ctx->linux_aio;
}
LinuxAioState *aio_get_linux_aio(AioContext *ctx)
{
assert(ctx->linux_aio);
return ctx->linux_aio;
}
#endif
#ifdef CONFIG_LINUX_IO_URING
LuringState *aio_setup_linux_io_uring(AioContext *ctx, Error **errp)
{
if (ctx->linux_io_uring) {
return ctx->linux_io_uring;
}
ctx->linux_io_uring = luring_init(errp);
if (!ctx->linux_io_uring) {
return NULL;
}
luring_attach_aio_context(ctx->linux_io_uring, ctx);
return ctx->linux_io_uring;
}
LuringState *aio_get_linux_io_uring(AioContext *ctx)
{
assert(ctx->linux_io_uring);
return ctx->linux_io_uring;
}
#endif
void aio_notify(AioContext *ctx)
{
/*
* Write e.g. bh->flags before writing ctx->notified. Pairs with smp_mb in
* aio_notify_accept.
*/
smp_wmb();
qatomic_set(&ctx->notified, true);
/*
* Write ctx->notified before reading ctx->notify_me. Pairs
* with smp_mb in aio_ctx_prepare or aio_poll.
*/
smp_mb();
if (qatomic_read(&ctx->notify_me)) {
event_notifier_set(&ctx->notifier);
}
}
void aio_notify_accept(AioContext *ctx)
{
qatomic_set(&ctx->notified, false);
/*
* Write ctx->notified before reading e.g. bh->flags. Pairs with smp_wmb
* in aio_notify.
*/
smp_mb();
}
static void aio_timerlist_notify(void *opaque, QEMUClockType type)
{
aio_notify(opaque);
}
static void aio_context_notifier_cb(EventNotifier *e)
{
AioContext *ctx = container_of(e, AioContext, notifier);
event_notifier_test_and_clear(&ctx->notifier);
}
/* Returns true if aio_notify() was called (e.g. a BH was scheduled) */
static bool aio_context_notifier_poll(void *opaque)
{
EventNotifier *e = opaque;
AioContext *ctx = container_of(e, AioContext, notifier);
return qatomic_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 */
qatomic_set(&co->scheduled, NULL);
qemu_aio_coroutine_enter(ctx, 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));
QSLIST_INIT(&ctx->bh_list);
QSIMPLEQ_INIT(&ctx->bh_slice_list);
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,
aio_context_notifier_cb,
aio_context_notifier_poll);
#ifdef CONFIG_LINUX_AIO
ctx->linux_aio = NULL;
#endif
#ifdef CONFIG_LINUX_IO_URING
ctx->linux_io_uring = 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 = qatomic_cmpxchg(&co->scheduled, NULL,
__func__);
if (scheduled) {
fprintf(stderr,
"%s: Co-routine was already scheduled in '%s'\n",
__func__, scheduled);
abort();
}
/* The coroutine might run and release the last ctx reference before we
* invoke qemu_bh_schedule(). Take a reference to keep ctx alive until
* we're done.
*/
aio_context_ref(ctx);
QSLIST_INSERT_HEAD_ATOMIC(&ctx->scheduled_coroutines,
co, co_scheduled_next);
qemu_bh_schedule(ctx->co_schedule_bh);
aio_context_unref(ctx);
}
typedef struct AioCoRescheduleSelf {
Coroutine *co;
AioContext *new_ctx;
} AioCoRescheduleSelf;
static void aio_co_reschedule_self_bh(void *opaque)
{
AioCoRescheduleSelf *data = opaque;
aio_co_schedule(data->new_ctx, data->co);
}
void coroutine_fn aio_co_reschedule_self(AioContext *new_ctx)
{
AioContext *old_ctx = qemu_get_current_aio_context();
if (old_ctx != new_ctx) {
AioCoRescheduleSelf data = {
.co = qemu_coroutine_self(),
.new_ctx = new_ctx,
};
/*
* We can't directly schedule the coroutine in the target context
* because this would be racy: The other thread could try to enter the
* coroutine before it has yielded in this one.
*/
aio_bh_schedule_oneshot(old_ctx, aio_co_reschedule_self_bh, &data);
qemu_coroutine_yield();
}
}
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 = qatomic_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);
}
