diff options
Diffstat (limited to 'qemu-aio.h')
| -rw-r--r-- | qemu-aio.h | 206 |
1 files changed, 192 insertions, 14 deletions
diff --git a/qemu-aio.h b/qemu-aio.h index bfdd35f02c..1b7eb6ef5b 100644 --- a/qemu-aio.h +++ b/qemu-aio.h @@ -15,7 +15,8 @@ #define QEMU_AIO_H #include "qemu-common.h" -#include "qemu-char.h" +#include "qemu-queue.h" +#include "event_notifier.h" typedef struct BlockDriverAIOCB BlockDriverAIOCB; typedef void BlockDriverCompletionFunc(void *opaque, int ret); @@ -38,20 +39,162 @@ 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 (AioFlushHandler)(void *opaque); +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 qemu_aio_flush(void); +void aio_flush(AioContext *ctx); -/* Wait for a single AIO completion to occur. This function will wait - * until a single AIO event has completed and it will ensure something - * has moved before returning. This can issue new pending aio as - * result of executing I/O completion or bh callbacks. +/* Return whether there are any pending callbacks from the GSource + * attached to the AioContext. * - * Return whether there is still any pending AIO operation. */ -bool qemu_aio_wait(void); + * 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 @@ -60,10 +203,45 @@ bool qemu_aio_wait(void); * Code that invokes AIO completion functions should rely on this function * instead of qemu_set_fd_handler[2]. */ -int qemu_aio_set_fd_handler(int fd, - IOHandler *io_read, - IOHandler *io_write, - AioFlushHandler *io_flush, - void *opaque); +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 |