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/*
* AioContext wait support
*
* Copyright (C) 2018 Red Hat, Inc.
*
* 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 "qemu/main-loop.h"
#include "block/aio-wait.h"
AioWait global_aio_wait;
static void dummy_bh_cb(void *opaque)
{
/* The point is to make AIO_WAIT_WHILE()'s aio_poll() return */
}
void aio_wait_kick(void)
{
/*
* Paired with smp_mb in AIO_WAIT_WHILE. Here we have:
* write(condition);
* aio_wait_kick() {
* smp_mb();
* read(num_waiters);
* }
*
* And in AIO_WAIT_WHILE:
* write(num_waiters);
* smp_mb();
* read(condition);
*/
smp_mb();
if (qatomic_read(&global_aio_wait.num_waiters)) {
aio_bh_schedule_oneshot(qemu_get_aio_context(), dummy_bh_cb, NULL);
}
}
typedef struct {
bool done;
QEMUBHFunc *cb;
void *opaque;
} AioWaitBHData;
/* Context: BH in IOThread */
static void aio_wait_bh(void *opaque)
{
AioWaitBHData *data = opaque;
data->cb(data->opaque);
data->done = true;
aio_wait_kick();
}
void aio_wait_bh_oneshot(AioContext *ctx, QEMUBHFunc *cb, void *opaque)
{
AioWaitBHData data = {
.cb = cb,
.opaque = opaque,
};
assert(qemu_get_current_aio_context() == qemu_get_aio_context());
aio_bh_schedule_oneshot(ctx, aio_wait_bh, &data);
AIO_WAIT_WHILE(ctx, !data.done);
}
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