aio_co_wake provides the infrastructure to start a coroutine on a "home" AioContext. It will be used by CoMutex and CoQueue, so that coroutines don't jump from one context to another when they go to sleep on a mutex or waitqueue. However, it can also be used as a more efficient alternative to one-shot bottom halves, and saves the effort of tracking which AioContext a coroutine is running on. aio_co_schedule is the part of aio_co_wake that starts a coroutine on a remove AioContext, but it is also useful to implement e.g. bdrv_set_aio_context callbacks. The implementation of aio_co_schedule is based on a lock-free multiple-producer, single-consumer queue. The multiple producers use cmpxchg to add to a LIFO stack. The consumer (a per-AioContext bottom half) grabs all items added so far, inverts the list to make it FIFO, and goes through it one item at a time until it's empty. The data structure was inspired by OSv, which uses it in the very code we'll "port" to QEMU for the thread-safe CoMutex. Most of the new code is really tests. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Reviewed-by: Fam Zheng <famz@redhat.com> Message-id: 20170213135235.12274-3-pbonzini@redhat.com Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
67 lines
2.2 KiB
C
67 lines
2.2 KiB
C
/*
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* Coroutine internals
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*
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* Copyright (c) 2011 Kevin Wolf <kwolf@redhat.com>
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*/
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#ifndef QEMU_COROUTINE_INT_H
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#define QEMU_COROUTINE_INT_H
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#include "qemu/queue.h"
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#include "qemu/coroutine.h"
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#define COROUTINE_STACK_SIZE (1 << 20)
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typedef enum {
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COROUTINE_YIELD = 1,
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COROUTINE_TERMINATE = 2,
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COROUTINE_ENTER = 3,
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} CoroutineAction;
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struct Coroutine {
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CoroutineEntry *entry;
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void *entry_arg;
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Coroutine *caller;
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/* Only used when the coroutine has terminated. */
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QSLIST_ENTRY(Coroutine) pool_next;
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size_t locks_held;
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/* Coroutines that should be woken up when we yield or terminate.
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* Only used when the coroutine is running.
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*/
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QSIMPLEQ_HEAD(, Coroutine) co_queue_wakeup;
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/* Only used when the coroutine has yielded. */
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AioContext *ctx;
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QSIMPLEQ_ENTRY(Coroutine) co_queue_next;
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QSLIST_ENTRY(Coroutine) co_scheduled_next;
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};
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Coroutine *qemu_coroutine_new(void);
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void qemu_coroutine_delete(Coroutine *co);
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CoroutineAction qemu_coroutine_switch(Coroutine *from, Coroutine *to,
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CoroutineAction action);
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void coroutine_fn qemu_co_queue_run_restart(Coroutine *co);
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#endif
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