Start introducing AioContext, which will let us remove globals from aio.c/async.c, and introduce multiple I/O threads. The bottom half functions now take an additional AioContext argument. A bottom half is created with a specific AioContext that remains the same throughout the lifetime. qemu_bh_new is just a wrapper that uses a global context. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
164 lines
5.3 KiB
C
164 lines
5.3 KiB
C
/*
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* QEMU aio implementation
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*
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* Copyright IBM, Corp. 2008
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*
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* Authors:
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* Anthony Liguori <aliguori@us.ibm.com>
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*
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* This work is licensed under the terms of the GNU GPL, version 2. See
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* the COPYING file in the top-level directory.
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*
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*/
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#ifndef QEMU_AIO_H
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#define QEMU_AIO_H
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#include "qemu-common.h"
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#include "event_notifier.h"
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typedef struct BlockDriverAIOCB BlockDriverAIOCB;
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typedef void BlockDriverCompletionFunc(void *opaque, int ret);
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typedef struct AIOPool {
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void (*cancel)(BlockDriverAIOCB *acb);
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int aiocb_size;
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BlockDriverAIOCB *free_aiocb;
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} AIOPool;
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struct BlockDriverAIOCB {
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AIOPool *pool;
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BlockDriverState *bs;
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BlockDriverCompletionFunc *cb;
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void *opaque;
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BlockDriverAIOCB *next;
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};
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void *qemu_aio_get(AIOPool *pool, BlockDriverState *bs,
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BlockDriverCompletionFunc *cb, void *opaque);
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void qemu_aio_release(void *p);
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typedef struct AioHandler AioHandler;
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typedef void QEMUBHFunc(void *opaque);
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typedef void IOHandler(void *opaque);
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typedef struct AioContext {
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/* Anchor of the list of Bottom Halves belonging to the context */
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struct QEMUBH *first_bh;
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/* A simple lock used to protect the first_bh list, and ensure that
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* no callbacks are removed while we're walking and dispatching callbacks.
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*/
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int walking_bh;
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} AioContext;
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/* Returns 1 if there are still outstanding AIO requests; 0 otherwise */
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typedef int (AioFlushEventNotifierHandler)(EventNotifier *e);
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/**
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* aio_context_new: Allocate a new AioContext.
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*
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* AioContext provide a mini event-loop that can be waited on synchronously.
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* They also provide bottom halves, a service to execute a piece of code
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* as soon as possible.
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*/
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AioContext *aio_context_new(void);
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/**
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* aio_bh_new: Allocate a new bottom half structure.
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*
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* Bottom halves are lightweight callbacks whose invocation is guaranteed
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* to be wait-free, thread-safe and signal-safe. The #QEMUBH structure
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* is opaque and must be allocated prior to its use.
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*/
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QEMUBH *aio_bh_new(AioContext *ctx, QEMUBHFunc *cb, void *opaque);
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/**
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* aio_bh_poll: Poll bottom halves for an AioContext.
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*
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* These are internal functions used by the QEMU main loop.
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*/
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int aio_bh_poll(AioContext *ctx);
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void aio_bh_update_timeout(AioContext *ctx, uint32_t *timeout);
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/**
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* qemu_bh_schedule: Schedule a bottom half.
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*
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* Scheduling a bottom half interrupts the main loop and causes the
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* execution of the callback that was passed to qemu_bh_new.
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*
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* Bottom halves that are scheduled from a bottom half handler are instantly
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* invoked. This can create an infinite loop if a bottom half handler
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* schedules itself.
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*
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* @bh: The bottom half to be scheduled.
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*/
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void qemu_bh_schedule(QEMUBH *bh);
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/**
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* qemu_bh_cancel: Cancel execution of a bottom half.
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*
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* Canceling execution of a bottom half undoes the effect of calls to
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* qemu_bh_schedule without freeing its resources yet. While cancellation
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* itself is also wait-free and thread-safe, it can of course race with the
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* loop that executes bottom halves unless you are holding the iothread
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* mutex. This makes it mostly useless if you are not holding the mutex.
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*
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* @bh: The bottom half to be canceled.
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*/
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void qemu_bh_cancel(QEMUBH *bh);
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/**
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*qemu_bh_delete: Cancel execution of a bottom half and free its resources.
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*
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* Deleting a bottom half frees the memory that was allocated for it by
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* qemu_bh_new. It also implies canceling the bottom half if it was
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* scheduled.
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*
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* @bh: The bottom half to be deleted.
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*/
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void qemu_bh_delete(QEMUBH *bh);
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/* Flush any pending AIO operation. This function will block until all
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* outstanding AIO operations have been completed or cancelled. */
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void qemu_aio_flush(void);
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/* Wait for a single AIO completion to occur. This function will wait
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* until a single AIO event has completed and it will ensure something
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* has moved before returning. This can issue new pending aio as
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* result of executing I/O completion or bh callbacks.
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*
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* Return whether there is still any pending AIO operation. */
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bool qemu_aio_wait(void);
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#ifdef CONFIG_POSIX
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/* Returns 1 if there are still outstanding AIO requests; 0 otherwise */
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typedef int (AioFlushHandler)(void *opaque);
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/* Register a file descriptor and associated callbacks. Behaves very similarly
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* to qemu_set_fd_handler2. Unlike qemu_set_fd_handler2, these callbacks will
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* be invoked when using either qemu_aio_wait() or qemu_aio_flush().
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*
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* Code that invokes AIO completion functions should rely on this function
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* instead of qemu_set_fd_handler[2].
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*/
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void qemu_aio_set_fd_handler(int fd,
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IOHandler *io_read,
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IOHandler *io_write,
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AioFlushHandler *io_flush,
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void *opaque);
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#endif
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/* Register an event notifier and associated callbacks. Behaves very similarly
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* to event_notifier_set_handler. Unlike event_notifier_set_handler, these callbacks
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* will be invoked when using either qemu_aio_wait() or qemu_aio_flush().
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*
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* Code that invokes AIO completion functions should rely on this function
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* instead of event_notifier_set_handler.
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*/
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void qemu_aio_set_event_notifier(EventNotifier *notifier,
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EventNotifierHandler *io_read,
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AioFlushEventNotifierHandler *io_flush);
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#endif
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