From cd9ba1ebcf0439457f22b75b38533f6634f23c5f Mon Sep 17 00:00:00 2001 From: Paolo Bonzini Date: Mon, 24 Sep 2012 14:57:22 +0200 Subject: [PATCH] aio: prepare for introducing GSource-based dispatch This adds a GPollFD to each AioHandler. It will then be possible to attach these GPollFDs to a GSource, and from there to the main loop. aio_wait examines the GPollFDs and avoids calling select() if any is set (similar to what it does if bottom halves are available). Signed-off-by: Paolo Bonzini --- aio.c | 93 ++++++++++++++++++++++++++++++++++++++++++++++-------- qemu-aio.h | 7 ++++ 2 files changed, 87 insertions(+), 13 deletions(-) diff --git a/aio.c b/aio.c index 1d5e0c62ce..44247224e2 100644 --- a/aio.c +++ b/aio.c @@ -20,7 +20,7 @@ struct AioHandler { - int fd; + GPollFD pfd; IOHandler *io_read; IOHandler *io_write; AioFlushHandler *io_flush; @@ -34,7 +34,7 @@ static AioHandler *find_aio_handler(AioContext *ctx, int fd) AioHandler *node; QLIST_FOREACH(node, &ctx->aio_handlers, node) { - if (node->fd == fd) + if (node->pfd.fd == fd) if (!node->deleted) return node; } @@ -57,9 +57,10 @@ void aio_set_fd_handler(AioContext *ctx, if (!io_read && !io_write) { if (node) { /* If the lock is held, just mark the node as deleted */ - if (ctx->walking_handlers) + if (ctx->walking_handlers) { node->deleted = 1; - else { + node->pfd.revents = 0; + } else { /* Otherwise, delete it for real. We can't just mark it as * deleted because deleted nodes are only cleaned up after * releasing the walking_handlers lock. @@ -72,7 +73,7 @@ void aio_set_fd_handler(AioContext *ctx, if (node == NULL) { /* Alloc and insert if it's not already there */ node = g_malloc0(sizeof(AioHandler)); - node->fd = fd; + node->pfd.fd = fd; QLIST_INSERT_HEAD(&ctx->aio_handlers, node, node); } /* Update handler with latest information */ @@ -80,6 +81,9 @@ void aio_set_fd_handler(AioContext *ctx, node->io_write = io_write; node->io_flush = io_flush; node->opaque = opaque; + + node->pfd.events = (io_read ? G_IO_IN | G_IO_HUP : 0); + node->pfd.events |= (io_write ? G_IO_OUT : 0); } } @@ -93,6 +97,32 @@ void aio_set_event_notifier(AioContext *ctx, (AioFlushHandler *)io_flush, notifier); } +bool aio_pending(AioContext *ctx) +{ + AioHandler *node; + + QLIST_FOREACH(node, &ctx->aio_handlers, node) { + int revents; + + /* + * FIXME: right now we cannot get G_IO_HUP and G_IO_ERR because + * main-loop.c is still select based (due to the slirp legacy). + * If main-loop.c ever switches to poll, G_IO_ERR should be + * tested too. Dispatching G_IO_ERR to both handlers should be + * okay, since handlers need to be ready for spurious wakeups. + */ + revents = node->pfd.revents & node->pfd.events; + if (revents & (G_IO_IN | G_IO_HUP | G_IO_ERR) && node->io_read) { + return true; + } + if (revents & (G_IO_OUT | G_IO_ERR) && node->io_write) { + return true; + } + } + + return false; +} + bool aio_poll(AioContext *ctx, bool blocking) { static struct timeval tv0; @@ -114,6 +144,43 @@ bool aio_poll(AioContext *ctx, bool blocking) progress = true; } + /* + * Then dispatch any pending callbacks from the GSource. + * + * We have to walk very carefully in case qemu_aio_set_fd_handler is + * called while we're walking. + */ + node = QLIST_FIRST(&ctx->aio_handlers); + while (node) { + AioHandler *tmp; + int revents; + + ctx->walking_handlers++; + + revents = node->pfd.revents & node->pfd.events; + node->pfd.revents = 0; + + /* See comment in aio_pending. */ + if (revents & (G_IO_IN | G_IO_HUP | G_IO_ERR) && node->io_read) { + node->io_read(node->opaque); + progress = true; + } + if (revents & (G_IO_OUT | G_IO_ERR) && node->io_write) { + node->io_write(node->opaque); + progress = true; + } + + tmp = node; + node = QLIST_NEXT(node, node); + + ctx->walking_handlers--; + + if (!ctx->walking_handlers && tmp->deleted) { + QLIST_REMOVE(tmp, node); + g_free(tmp); + } + } + if (progress && !blocking) { return true; } @@ -137,12 +204,12 @@ bool aio_poll(AioContext *ctx, bool blocking) busy = true; } if (!node->deleted && node->io_read) { - FD_SET(node->fd, &rdfds); - max_fd = MAX(max_fd, node->fd + 1); + FD_SET(node->pfd.fd, &rdfds); + max_fd = MAX(max_fd, node->pfd.fd + 1); } if (!node->deleted && node->io_write) { - FD_SET(node->fd, &wrfds); - max_fd = MAX(max_fd, node->fd + 1); + FD_SET(node->pfd.fd, &wrfds); + max_fd = MAX(max_fd, node->pfd.fd + 1); } } @@ -167,16 +234,16 @@ bool aio_poll(AioContext *ctx, bool blocking) ctx->walking_handlers++; if (!node->deleted && - FD_ISSET(node->fd, &rdfds) && + FD_ISSET(node->pfd.fd, &rdfds) && node->io_read) { - progress = true; node->io_read(node->opaque); + progress = true; } if (!node->deleted && - FD_ISSET(node->fd, &wrfds) && + FD_ISSET(node->pfd.fd, &wrfds) && node->io_write) { - progress = true; node->io_write(node->opaque); + progress = true; } tmp = node; diff --git a/qemu-aio.h b/qemu-aio.h index f19201e7ca..ac248962fe 100644 --- a/qemu-aio.h +++ b/qemu-aio.h @@ -133,6 +133,13 @@ void qemu_bh_delete(QEMUBH *bh); * 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. *