--- /dev/null
+/*
+ * QEMU aio implementation
+ *
+ * Copyright IBM, Corp. 2008
+ *
+ * Authors:
+ * Anthony Liguori <aliguori@us.ibm.com>
+ *
+ * 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;
+}
Code Review / kvmfornfv.git / blobdiff