#define QEMU_AIO_H
#include "qemu-common.h"
-#include "qemu-char.h"
+#include "qemu-queue.h"
#include "event_notifier.h"
typedef struct BlockDriverAIOCB BlockDriverAIOCB;
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 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 */
* Code that invokes AIO completion functions should rely on this function
* instead of qemu_set_fd_handler[2].
*/
-void 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
* 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
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