b493317d34
Uses the same select/WSAEventSelect scheme as main-loop.c. WSAEventSelect() is edge-triggered, so it cannot be used directly, but it is still used as a way to exit from a blocking g_poll(). Before g_poll() is called, we poll sockets with a non-blocking select() to achieve the level-triggered semantics we require: if a socket is ready, the g_poll() is made non-blocking too. Based on a patch from Or Goshen. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
326 lines
10 KiB
C
326 lines
10 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/typedefs.h"
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#include "qemu-common.h"
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#include "qemu/queue.h"
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#include "qemu/event_notifier.h"
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#include "qemu/thread.h"
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#include "qemu/rfifolock.h"
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#include "qemu/timer.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 AIOCBInfo {
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void (*cancel)(BlockDriverAIOCB *acb);
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size_t aiocb_size;
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} AIOCBInfo;
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struct BlockDriverAIOCB {
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const AIOCBInfo *aiocb_info;
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BlockDriverState *bs;
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BlockDriverCompletionFunc *cb;
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void *opaque;
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};
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void *qemu_aio_get(const AIOCBInfo *aiocb_info, 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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struct AioContext {
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GSource source;
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/* Protects all fields from multi-threaded access */
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RFifoLock lock;
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/* The list of registered AIO handlers */
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QLIST_HEAD(, AioHandler) aio_handlers;
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/* This is a simple lock used to protect the aio_handlers list.
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* Specifically, it's used to ensure that no callbacks are removed while
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* we're walking and dispatching callbacks.
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*/
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int walking_handlers;
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/* Used to avoid unnecessary event_notifier_set calls in aio_notify.
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* Writes protected by lock or BQL, reads are lockless.
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*/
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bool dispatching;
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/* lock to protect between bh's adders and deleter */
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QemuMutex bh_lock;
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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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/* Used for aio_notify. */
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EventNotifier notifier;
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/* GPollFDs for aio_poll() */
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GArray *pollfds;
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/* Thread pool for performing work and receiving completion callbacks */
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struct ThreadPool *thread_pool;
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/* TimerLists for calling timers - one per clock type */
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QEMUTimerListGroup tlg;
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};
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/* Used internally to synchronize aio_poll against qemu_bh_schedule. */
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void aio_set_dispatching(AioContext *ctx, bool dispatching);
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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_context_ref:
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* @ctx: The AioContext to operate on.
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*
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* Add a reference to an AioContext.
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*/
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void aio_context_ref(AioContext *ctx);
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/**
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* aio_context_unref:
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* @ctx: The AioContext to operate on.
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*
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* Drop a reference to an AioContext.
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*/
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void aio_context_unref(AioContext *ctx);
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/* Take ownership of the AioContext. If the AioContext will be shared between
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* threads, a thread must have ownership when calling aio_poll().
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*
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* Note that multiple threads calling aio_poll() means timers, BHs, and
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* callbacks may be invoked from a different thread than they were registered
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* from. Therefore, code must use AioContext acquire/release or use
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* fine-grained synchronization to protect shared state if other threads will
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* be accessing it simultaneously.
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*/
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void aio_context_acquire(AioContext *ctx);
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/* Relinquish ownership of the AioContext. */
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void aio_context_release(AioContext *ctx);
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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_notify: Force processing of pending events.
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*
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* Similar to signaling a condition variable, aio_notify forces
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* aio_wait to exit, so that the next call will re-examine pending events.
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* The caller of aio_notify will usually call aio_wait again very soon,
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* or go through another iteration of the GLib main loop. Hence, aio_notify
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* also has the side effect of recalculating the sets of file descriptors
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* that the main loop waits for.
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*
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* Calling aio_notify is rarely necessary, because for example scheduling
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* a bottom half calls it already.
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*/
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void aio_notify(AioContext *ctx);
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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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* And notice that multiple occurrences of aio_bh_poll cannot
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* be called concurrently
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*/
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int aio_bh_poll(AioContext *ctx);
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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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* This func is async. The bottom half will do the delete action at the finial
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* end.
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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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/* Return whether there are any pending callbacks from the GSource
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* attached to the AioContext, before g_poll is invoked.
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*
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* This is used internally in the implementation of the GSource.
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*/
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bool aio_prepare(AioContext *ctx);
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/* Return whether there are any pending callbacks from the GSource
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* attached to the AioContext, after g_poll is invoked.
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*
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* This is used internally in the implementation of the GSource.
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*/
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bool aio_pending(AioContext *ctx);
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/* Dispatch any pending callbacks from the GSource attached to the AioContext.
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*
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* This is used internally in the implementation of the GSource.
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*/
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bool aio_dispatch(AioContext *ctx);
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/* Progress in completing AIO work to occur. This can issue new pending
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* aio as a result of executing I/O completion or bh callbacks.
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*
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* Return whether any progress was made by executing AIO or bottom half
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* handlers. If @blocking == true, this should always be true except
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* if someone called aio_notify.
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*
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* If there are no pending bottom halves, but there are pending AIO
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* operations, it may not be possible to make any progress without
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* blocking. If @blocking is true, this function will wait until one
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* or more AIO events have completed, to ensure something has moved
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* before returning.
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*/
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bool aio_poll(AioContext *ctx, bool blocking);
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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 aio_poll().
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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 aio_set_fd_handler(AioContext *ctx,
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int fd,
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IOHandler *io_read,
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IOHandler *io_write,
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void *opaque);
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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 aio_poll().
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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 aio_set_event_notifier(AioContext *ctx,
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EventNotifier *notifier,
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EventNotifierHandler *io_read);
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/* Return a GSource that lets the main loop poll the file descriptors attached
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* to this AioContext.
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*/
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GSource *aio_get_g_source(AioContext *ctx);
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/* Return the ThreadPool bound to this AioContext */
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struct ThreadPool *aio_get_thread_pool(AioContext *ctx);
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/**
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* aio_timer_new:
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* @ctx: the aio context
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* @type: the clock type
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* @scale: the scale
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* @cb: the callback to call on timer expiry
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* @opaque: the opaque pointer to pass to the callback
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*
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* Allocate a new timer attached to the context @ctx.
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* The function is responsible for memory allocation.
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*
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* The preferred interface is aio_timer_init. Use that
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* unless you really need dynamic memory allocation.
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*
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* Returns: a pointer to the new timer
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*/
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static inline QEMUTimer *aio_timer_new(AioContext *ctx, QEMUClockType type,
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int scale,
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QEMUTimerCB *cb, void *opaque)
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{
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return timer_new_tl(ctx->tlg.tl[type], scale, cb, opaque);
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}
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/**
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* aio_timer_init:
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* @ctx: the aio context
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* @ts: the timer
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* @type: the clock type
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* @scale: the scale
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* @cb: the callback to call on timer expiry
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* @opaque: the opaque pointer to pass to the callback
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*
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* Initialise a new timer attached to the context @ctx.
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* The caller is responsible for memory allocation.
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*/
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static inline void aio_timer_init(AioContext *ctx,
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QEMUTimer *ts, QEMUClockType type,
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int scale,
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QEMUTimerCB *cb, void *opaque)
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{
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timer_init(ts, ctx->tlg.tl[type], scale, cb, opaque);
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}
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/**
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* aio_compute_timeout:
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* @ctx: the aio context
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*
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* Compute the timeout that a blocking aio_poll should use.
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*/
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int64_t aio_compute_timeout(AioContext *ctx);
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#endif
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