From 3f2546b2ef55b661fd8dd69682b38992225e86f6 Mon Sep 17 00:00:00 2001 From: fishsoupisgood Date: Mon, 29 Apr 2019 01:17:54 +0100 Subject: Initial import of qemu-2.4.1 --- aio-posix.c | 299 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 299 insertions(+) create mode 100644 aio-posix.c (limited to 'aio-posix.c') diff --git a/aio-posix.c b/aio-posix.c new file mode 100644 index 00000000..d4770336 --- /dev/null +++ b/aio-posix.c @@ -0,0 +1,299 @@ +/* + * QEMU aio implementation + * + * Copyright IBM, Corp. 2008 + * + * Authors: + * Anthony Liguori + * + * This work is licensed under the terms of the GNU GPL, version 2. See + * the COPYING file in the top-level directory. + * + * Contributions after 2012-01-13 are licensed under the terms of the + * GNU GPL, version 2 or (at your option) any later version. + */ + +#include "qemu-common.h" +#include "block/block.h" +#include "qemu/queue.h" +#include "qemu/sockets.h" + +struct AioHandler +{ + GPollFD pfd; + IOHandler *io_read; + IOHandler *io_write; + int deleted; + void *opaque; + QLIST_ENTRY(AioHandler) node; +}; + +static AioHandler *find_aio_handler(AioContext *ctx, int fd) +{ + AioHandler *node; + + QLIST_FOREACH(node, &ctx->aio_handlers, node) { + if (node->pfd.fd == fd) + if (!node->deleted) + return node; + } + + return NULL; +} + +void aio_set_fd_handler(AioContext *ctx, + int fd, + IOHandler *io_read, + IOHandler *io_write, + void *opaque) +{ + AioHandler *node; + + node = find_aio_handler(ctx, fd); + + /* Are we deleting the fd handler? */ + if (!io_read && !io_write) { + if (node) { + g_source_remove_poll(&ctx->source, &node->pfd); + + /* If the lock is held, just mark the node as deleted */ + if (ctx->walking_handlers) { + node->deleted = 1; + 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. + */ + QLIST_REMOVE(node, node); + g_free(node); + } + } + } else { + if (node == NULL) { + /* Alloc and insert if it's not already there */ + node = g_new0(AioHandler, 1); + node->pfd.fd = fd; + QLIST_INSERT_HEAD(&ctx->aio_handlers, node, node); + + g_source_add_poll(&ctx->source, &node->pfd); + } + /* Update handler with latest information */ + node->io_read = io_read; + node->io_write = io_write; + node->opaque = opaque; + + node->pfd.events = (io_read ? G_IO_IN | G_IO_HUP | G_IO_ERR : 0); + node->pfd.events |= (io_write ? G_IO_OUT | G_IO_ERR : 0); + } + + aio_notify(ctx); +} + +void aio_set_event_notifier(AioContext *ctx, + EventNotifier *notifier, + EventNotifierHandler *io_read) +{ + aio_set_fd_handler(ctx, event_notifier_get_fd(notifier), + (IOHandler *)io_read, NULL, notifier); +} + +bool aio_prepare(AioContext *ctx) +{ + return false; +} + +bool aio_pending(AioContext *ctx) +{ + AioHandler *node; + + QLIST_FOREACH(node, &ctx->aio_handlers, node) { + int revents; + + 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_dispatch(AioContext *ctx) +{ + AioHandler *node; + bool progress = false; + + /* + * If there are callbacks left that have been queued, we need to call them. + * Do not call select in this case, because it is possible that the caller + * does not need a complete flush (as is the case for aio_poll loops). + */ + if (aio_bh_poll(ctx)) { + progress = true; + } + + /* + * We have to walk very carefully in case 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; + + if (!node->deleted && + (revents & (G_IO_IN | G_IO_HUP | G_IO_ERR)) && + node->io_read) { + node->io_read(node->opaque); + + /* aio_notify() does not count as progress */ + if (node->opaque != &ctx->notifier) { + progress = true; + } + } + if (!node->deleted && + (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); + } + } + + /* Run our timers */ + progress |= timerlistgroup_run_timers(&ctx->tlg); + + return progress; +} + +/* These thread-local variables are used only in a small part of aio_poll + * around the call to the poll() system call. In particular they are not + * used while aio_poll is performing callbacks, which makes it much easier + * to think about reentrancy! + * + * Stack-allocated arrays would be perfect but they have size limitations; + * heap allocation is expensive enough that we want to reuse arrays across + * calls to aio_poll(). And because poll() has to be called without holding + * any lock, the arrays cannot be stored in AioContext. Thread-local data + * has none of the disadvantages of these three options. + */ +static __thread GPollFD *pollfds; +static __thread AioHandler **nodes; +static __thread unsigned npfd, nalloc; +static __thread Notifier pollfds_cleanup_notifier; + +static void pollfds_cleanup(Notifier *n, void *unused) +{ + g_assert(npfd == 0); + g_free(pollfds); + g_free(nodes); + nalloc = 0; +} + +static void add_pollfd(AioHandler *node) +{ + if (npfd == nalloc) { + if (nalloc == 0) { + pollfds_cleanup_notifier.notify = pollfds_cleanup; + qemu_thread_atexit_add(&pollfds_cleanup_notifier); + nalloc = 8; + } else { + g_assert(nalloc <= INT_MAX); + nalloc *= 2; + } + pollfds = g_renew(GPollFD, pollfds, nalloc); + nodes = g_renew(AioHandler *, nodes, nalloc); + } + nodes[npfd] = node; + pollfds[npfd] = (GPollFD) { + .fd = node->pfd.fd, + .events = node->pfd.events, + }; + npfd++; +} + +bool aio_poll(AioContext *ctx, bool blocking) +{ + AioHandler *node; + int i, ret; + bool progress; + int64_t timeout; + + aio_context_acquire(ctx); + progress = false; + + /* aio_notify can avoid the expensive event_notifier_set if + * everything (file descriptors, bottom halves, timers) will + * be re-evaluated before the next blocking poll(). This is + * already true when aio_poll is called with blocking == false; + * if blocking == true, it is only true after poll() returns, + * so disable the optimization now. + */ + if (blocking) { + atomic_add(&ctx->notify_me, 2); + } + + ctx->walking_handlers++; + + assert(npfd == 0); + + /* fill pollfds */ + QLIST_FOREACH(node, &ctx->aio_handlers, node) { + if (!node->deleted && node->pfd.events) { + add_pollfd(node); + } + } + + timeout = blocking ? aio_compute_timeout(ctx) : 0; + + /* wait until next event */ + if (timeout) { + aio_context_release(ctx); + } + ret = qemu_poll_ns((GPollFD *)pollfds, npfd, timeout); + if (blocking) { + atomic_sub(&ctx->notify_me, 2); + } + if (timeout) { + aio_context_acquire(ctx); + } + + aio_notify_accept(ctx); + + /* if we have any readable fds, dispatch event */ + if (ret > 0) { + for (i = 0; i < npfd; i++) { + nodes[i]->pfd.revents = pollfds[i].revents; + } + } + + npfd = 0; + ctx->walking_handlers--; + + /* Run dispatch even if there were no readable fds to run timers */ + if (aio_dispatch(ctx)) { + progress = true; + } + + aio_context_release(ctx); + + return progress; +} -- cgit v1.2.3