/*
* QEMU aio implementation
*
* Copyright IBM, Corp. 2008
*
* Authors:
* Anthony Liguori <aliguori@us.ibm.com>
*
* This work is licensed under the terms of the GNU GPL, version 2. See
* the COPYING file in the top-level directory.
*
*/
#ifndef QEMU_AIO_H
#define QEMU_AIO_H
#include "qemu-common.h"
#include "qemu-queue.h"
#include "event_notifier.h"
typedef struct BlockDriverAIOCB BlockDriverAIOCB;
typedef void BlockDriverCompletionFunc(void *opaque, int ret);
typedef struct AIOPool {
void (*cancel)(BlockDriverAIOCB *acb);
int aiocb_size;
BlockDriverAIOCB *free_aiocb;
} AIOPool;
struct BlockDriverAIOCB {
AIOPool *pool;
BlockDriverState *bs;
BlockDriverCompletionFunc *cb;
void *opaque;
BlockDriverAIOCB *next;
};
void *qemu_aio_get(AIOPool *pool, BlockDriverState *bs,
BlockDriverCompletionFunc *cb, void *opaque);
void qemu_aio_release(void *p);
typedef struct AioHandler AioHandler;
typedef void QEMUBHFunc(void *opaque);
typedef void IOHandler(void *opaque);
typedef struct AioContext {
GSource source;
/* The list of registered AIO handlers */
QLIST_HEAD(, AioHandler) aio_handlers;
/* This is a simple lock used to protect the aio_handlers list.
* Specifically, it's used to ensure that no callbacks are removed while
* we're walking and dispatching callbacks.
*/
int walking_handlers;
/* Anchor of the list of Bottom Halves belonging to the context */
struct QEMUBH *first_bh;
/* A simple lock used to protect the first_bh list, and ensure that
* no callbacks are removed while we're walking and dispatching callbacks.
*/
int walking_bh;
/* Used for aio_notify. */
EventNotifier notifier;
} AioContext;
/* Returns 1 if there are still outstanding AIO requests; 0 otherwise */
typedef int (AioFlushEventNotifierHandler)(EventNotifier *e);
/**
* aio_context_new: Allocate a new AioContext.
*
* AioContext provide a mini event-loop that can be waited on synchronously.
* They also provide bottom halves, a service to execute a piece of code
* as soon as possible.
*/
AioContext *aio_context_new(void);
/**
* aio_context_ref:
* @ctx: The AioContext to operate on.
*
* Add a reference to an AioContext.
*/
void aio_context_ref(AioContext *ctx);
/**
* aio_context_unref:
* @ctx: The AioContext to operate on.
*
* Drop a reference to an AioContext.
*/
void aio_context_unref(AioContext *ctx);
/**
* aio_bh_new: Allocate a new bottom half structure.
*
* Bottom halves are lightweight callbacks whose invocation is guaranteed
* to be wait-free, thread-safe and signal-safe. The #QEMUBH structure
* is opaque and must be allocated prior to its use.
*/
QEMUBH *aio_bh_new(AioContext *ctx, QEMUBHFunc *cb, void *opaque);
/**
* aio_notify: Force processing of pending events.
*
* Similar to signaling a condition variable, aio_notify forces
* aio_wait to exit, so that the next call will re-examine pending events.
* The caller of aio_notify will usually call aio_wait again very soon,
* or go through another iteration of the GLib main loop. Hence, aio_notify
* also has the side effect of recalculating the sets of file descriptors
* that the main loop waits for.
*
* Calling aio_notify is rarely necessary, because for example scheduling
* a bottom half calls it already.
*/
void aio_notify(AioContext *ctx);
/**
* aio_bh_poll: Poll bottom halves for an AioContext.
*
* These are internal functions used by the QEMU main loop.
*/
int aio_bh_poll(AioContext *ctx);
/**
* qemu_bh_schedule: Schedule a bottom half.
*
* Scheduling a bottom half interrupts the main loop and causes the
* execution of the callback that was passed to qemu_bh_new.
*
* Bottom halves that are scheduled from a bottom half handler are instantly
* invoked. This can create an infinite loop if a bottom half handler
* schedules itself.
*
* @bh: The bottom half to be scheduled.
*/
void qemu_bh_schedule(QEMUBH *bh);
/**
* qemu_bh_cancel: Cancel execution of a bottom half.
*
* Canceling execution of a bottom half undoes the effect of calls to
* qemu_bh_schedule without freeing its resources yet. While cancellation
* itself is also wait-free and thread-safe, it can of course race with the
* loop that executes bottom halves unless you are holding the iothread
* mutex. This makes it mostly useless if you are not holding the mutex.
*
* @bh: The bottom half to be canceled.
*/
void qemu_bh_cancel(QEMUBH *bh);
/**
*qemu_bh_delete: Cancel execution of a bottom half and free its resources.
*
* Deleting a bottom half frees the memory that was allocated for it by
* qemu_bh_new. It also implies canceling the bottom half if it was
* scheduled.
*
* @bh: The bottom half to be deleted.
*/
void qemu_bh_delete(QEMUBH *bh);
/* Flush any pending AIO operation. This function will block until all
* outstanding AIO operations have been completed or cancelled. */
void aio_flush(AioContext *ctx);
/* Return whether there are any pending callbacks from the GSource
* attached to the AioContext.
*
* This is used internally in the implementation of the GSource.
*/
bool aio_pending(AioContext *ctx);
/* Progress in completing AIO work to occur. This can issue new pending
* aio as a result of executing I/O completion or bh callbacks.
*
* If there is no pending AIO operation or completion (bottom half),
* return false. If there are pending bottom halves, return true.
*
* If there are no pending bottom halves, but there are pending AIO
* operations, it may not be possible to make any progress without
* blocking. If @blocking is true, this function will wait until one
* or more AIO events have completed, to ensure something has moved
* before returning.
*
* If @blocking is false, this function will also return false if the
* function cannot make any progress without blocking.
*/
bool aio_poll(AioContext *ctx, bool blocking);
#ifdef CONFIG_POSIX
/* Returns 1 if there are still outstanding AIO requests; 0 otherwise */
typedef int (AioFlushHandler)(void *opaque);
/* Register a file descriptor and associated callbacks. Behaves very similarly
* to qemu_set_fd_handler2. Unlike qemu_set_fd_handler2, these callbacks will
* be invoked when using either qemu_aio_wait() or qemu_aio_flush().
*
* Code that invokes AIO completion functions should rely on this function
* instead of qemu_set_fd_handler[2].
*/
void aio_set_fd_handler(AioContext *ctx,
int fd,
IOHandler *io_read,
IOHandler *io_write,
AioFlushHandler *io_flush,
void *opaque);
#endif
/* Register an event notifier and associated callbacks. Behaves very similarly
* to event_notifier_set_handler. Unlike event_notifier_set_handler, these callbacks
* will be invoked when using either qemu_aio_wait() or qemu_aio_flush().
*
* Code that invokes AIO completion functions should rely on this function
* instead of event_notifier_set_handler.
*/
void aio_set_event_notifier(AioContext *ctx,
EventNotifier *notifier,
EventNotifierHandler *io_read,
AioFlushEventNotifierHandler *io_flush);
/* Return a GSource that lets the main loop poll the file descriptors attached
* to this AioContext.
*/
GSource *aio_get_g_source(AioContext *ctx);
/* Functions to operate on the main QEMU AioContext. */
void qemu_aio_flush(void);
bool qemu_aio_wait(void);
void qemu_aio_set_event_notifier(EventNotifier *notifier,
EventNotifierHandler *io_read,
AioFlushEventNotifierHandler *io_flush);
#ifdef CONFIG_POSIX
void qemu_aio_set_fd_handler(int fd,
IOHandler *io_read,
IOHandler *io_write,
AioFlushHandler *io_flush,
void *opaque);
#endif
#endif
