/* * 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 AIOCBInfo { void (*cancel)(BlockDriverAIOCB *acb); size_t aiocb_size; } AIOCBInfo; struct BlockDriverAIOCB { const AIOCBInfo *aiocb_info; BlockDriverState *bs; BlockDriverCompletionFunc *cb; void *opaque; }; void *qemu_aio_get(const AIOCBInfo *aiocb_info, 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); /* 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 qemu_aio_wait(). * * 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 qemu_aio_wait(). * * 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. */ 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