Initial import of qemu-2.4.1HEADmaster

1 files changed, 299 insertions, 0 deletions

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   <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;
+}