block: move AioContext, QEMUTimer, main-loop to libqemuutil

AioContext is fairly self contained, the only dependency is QEMUTimer but
that in turn doesn't need anything else.  So move them out of block-obj-y
to avoid introducing a dependency from io/ to block-obj-y.

main-loop and its dependency iohandler also need to be moved, because
later in this series io/ will call iohandler_get_aio_context.

[Changed copyright "the QEMU team" to "other QEMU contributors" as
suggested by Daniel Berrange and agreed by Paolo.
--Stefan]

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Message-id: 20170213135235.12274-2-pbonzini@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

util/async.c

@@ -0,0 +1,423 @@
+/*
+ * Data plane event loop
+ *
+ * Copyright (c) 2003-2008 Fabrice Bellard
+ * Copyright (c) 2009-2017 QEMU contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#include "qemu/osdep.h"
+#include "qapi/error.h"
+#include "qemu-common.h"
+#include "block/aio.h"
+#include "block/thread-pool.h"
+#include "qemu/main-loop.h"
+#include "qemu/atomic.h"
+#include "block/raw-aio.h"
+
+/***********************************************************/
+/* bottom halves (can be seen as timers which expire ASAP) */
+
+struct QEMUBH {
+    AioContext *ctx;
+    QEMUBHFunc *cb;
+    void *opaque;
+    QEMUBH *next;
+    bool scheduled;
+    bool idle;
+    bool deleted;
+};
+
+void aio_bh_schedule_oneshot(AioContext *ctx, QEMUBHFunc *cb, void *opaque)
+{
+    QEMUBH *bh;
+    bh = g_new(QEMUBH, 1);
+    *bh = (QEMUBH){
+        .ctx = ctx,
+        .cb = cb,
+        .opaque = opaque,
+    };
+    qemu_lockcnt_lock(&ctx->list_lock);
+    bh->next = ctx->first_bh;
+    bh->scheduled = 1;
+    bh->deleted = 1;
+    /* Make sure that the members are ready before putting bh into list */
+    smp_wmb();
+    ctx->first_bh = bh;
+    qemu_lockcnt_unlock(&ctx->list_lock);
+    aio_notify(ctx);
+}
+
+QEMUBH *aio_bh_new(AioContext *ctx, QEMUBHFunc *cb, void *opaque)
+{
+    QEMUBH *bh;
+    bh = g_new(QEMUBH, 1);
+    *bh = (QEMUBH){
+        .ctx = ctx,
+        .cb = cb,
+        .opaque = opaque,
+    };
+    qemu_lockcnt_lock(&ctx->list_lock);
+    bh->next = ctx->first_bh;
+    /* Make sure that the members are ready before putting bh into list */
+    smp_wmb();
+    ctx->first_bh = bh;
+    qemu_lockcnt_unlock(&ctx->list_lock);
+    return bh;
+}
+
+void aio_bh_call(QEMUBH *bh)
+{
+    bh->cb(bh->opaque);
+}
+
+/* Multiple occurrences of aio_bh_poll cannot be called concurrently */
+int aio_bh_poll(AioContext *ctx)
+{
+    QEMUBH *bh, **bhp, *next;
+    int ret;
+    bool deleted = false;
+
+    qemu_lockcnt_inc(&ctx->list_lock);
+
+    ret = 0;
+    for (bh = atomic_rcu_read(&ctx->first_bh); bh; bh = next) {
+        next = atomic_rcu_read(&bh->next);
+        /* The atomic_xchg is paired with the one in qemu_bh_schedule.  The
+         * implicit memory barrier ensures that the callback sees all writes
+         * done by the scheduling thread.  It also ensures that the scheduling
+         * thread sees the zero before bh->cb has run, and thus will call
+         * aio_notify again if necessary.
+         */
+        if (atomic_xchg(&bh->scheduled, 0)) {
+            /* Idle BHs don't count as progress */
+            if (!bh->idle) {
+                ret = 1;
+            }
+            bh->idle = 0;
+            aio_bh_call(bh);
+        }
+        if (bh->deleted) {
+            deleted = true;
+        }
+    }
+
+    /* remove deleted bhs */
+    if (!deleted) {
+        qemu_lockcnt_dec(&ctx->list_lock);
+        return ret;
+    }
+
+    if (qemu_lockcnt_dec_and_lock(&ctx->list_lock)) {
+        bhp = &ctx->first_bh;
+        while (*bhp) {
+            bh = *bhp;
+            if (bh->deleted && !bh->scheduled) {
+                *bhp = bh->next;
+                g_free(bh);
+            } else {
+                bhp = &bh->next;
+            }
+        }
+        qemu_lockcnt_unlock(&ctx->list_lock);
+    }
+    return ret;
+}
+
+void qemu_bh_schedule_idle(QEMUBH *bh)
+{
+    bh->idle = 1;
+    /* Make sure that idle & any writes needed by the callback are done
+     * before the locations are read in the aio_bh_poll.
+     */
+    atomic_mb_set(&bh->scheduled, 1);
+}
+
+void qemu_bh_schedule(QEMUBH *bh)
+{
+    AioContext *ctx;
+
+    ctx = bh->ctx;
+    bh->idle = 0;
+    /* The memory barrier implicit in atomic_xchg makes sure that:
+     * 1. idle & any writes needed by the callback are done before the
+     *    locations are read in the aio_bh_poll.
+     * 2. ctx is loaded before scheduled is set and the callback has a chance
+     *    to execute.
+     */
+    if (atomic_xchg(&bh->scheduled, 1) == 0) {
+        aio_notify(ctx);
+    }
+}
+
+
+/* This func is async.
+ */
+void qemu_bh_cancel(QEMUBH *bh)
+{
+    bh->scheduled = 0;
+}
+
+/* This func is async.The bottom half will do the delete action at the finial
+ * end.
+ */
+void qemu_bh_delete(QEMUBH *bh)
+{
+    bh->scheduled = 0;
+    bh->deleted = 1;
+}
+
+int64_t
+aio_compute_timeout(AioContext *ctx)
+{
+    int64_t deadline;
+    int timeout = -1;
+    QEMUBH *bh;
+
+    for (bh = atomic_rcu_read(&ctx->first_bh); bh;
+         bh = atomic_rcu_read(&bh->next)) {
+        if (bh->scheduled) {
+            if (bh->idle) {
+                /* idle bottom halves will be polled at least
+                 * every 10ms */
+                timeout = 10000000;
+            } else {
+                /* non-idle bottom halves will be executed
+                 * immediately */
+                return 0;
+            }
+        }
+    }
+
+    deadline = timerlistgroup_deadline_ns(&ctx->tlg);
+    if (deadline == 0) {
+        return 0;
+    } else {
+        return qemu_soonest_timeout(timeout, deadline);
+    }
+}
+
+static gboolean
+aio_ctx_prepare(GSource *source, gint    *timeout)
+{
+    AioContext *ctx = (AioContext *) source;
+
+    atomic_or(&ctx->notify_me, 1);
+
+    /* We assume there is no timeout already supplied */
+    *timeout = qemu_timeout_ns_to_ms(aio_compute_timeout(ctx));
+
+    if (aio_prepare(ctx)) {
+        *timeout = 0;
+    }
+
+    return *timeout == 0;
+}
+
+static gboolean
+aio_ctx_check(GSource *source)
+{
+    AioContext *ctx = (AioContext *) source;
+    QEMUBH *bh;
+
+    atomic_and(&ctx->notify_me, ~1);
+    aio_notify_accept(ctx);
+
+    for (bh = ctx->first_bh; bh; bh = bh->next) {
+        if (bh->scheduled) {
+            return true;
+        }
+    }
+    return aio_pending(ctx) || (timerlistgroup_deadline_ns(&ctx->tlg) == 0);
+}
+
+static gboolean
+aio_ctx_dispatch(GSource     *source,
+                 GSourceFunc  callback,
+                 gpointer     user_data)
+{
+    AioContext *ctx = (AioContext *) source;
+
+    assert(callback == NULL);
+    aio_dispatch(ctx, true);
+    return true;
+}
+
+static void
+aio_ctx_finalize(GSource     *source)
+{
+    AioContext *ctx = (AioContext *) source;
+
+    thread_pool_free(ctx->thread_pool);
+
+#ifdef CONFIG_LINUX_AIO
+    if (ctx->linux_aio) {
+        laio_detach_aio_context(ctx->linux_aio, ctx);
+        laio_cleanup(ctx->linux_aio);
+        ctx->linux_aio = NULL;
+    }
+#endif
+
+    qemu_lockcnt_lock(&ctx->list_lock);
+    assert(!qemu_lockcnt_count(&ctx->list_lock));
+    while (ctx->first_bh) {
+        QEMUBH *next = ctx->first_bh->next;
+
+        /* qemu_bh_delete() must have been called on BHs in this AioContext */
+        assert(ctx->first_bh->deleted);
+
+        g_free(ctx->first_bh);
+        ctx->first_bh = next;
+    }
+    qemu_lockcnt_unlock(&ctx->list_lock);
+
+    aio_set_event_notifier(ctx, &ctx->notifier, false, NULL, NULL);
+    event_notifier_cleanup(&ctx->notifier);
+    qemu_rec_mutex_destroy(&ctx->lock);
+    qemu_lockcnt_destroy(&ctx->list_lock);
+    timerlistgroup_deinit(&ctx->tlg);
+}
+
+static GSourceFuncs aio_source_funcs = {
+    aio_ctx_prepare,
+    aio_ctx_check,
+    aio_ctx_dispatch,
+    aio_ctx_finalize
+};
+
+GSource *aio_get_g_source(AioContext *ctx)
+{
+    g_source_ref(&ctx->source);
+    return &ctx->source;
+}
+
+ThreadPool *aio_get_thread_pool(AioContext *ctx)
+{
+    if (!ctx->thread_pool) {
+        ctx->thread_pool = thread_pool_new(ctx);
+    }
+    return ctx->thread_pool;
+}
+
+#ifdef CONFIG_LINUX_AIO
+LinuxAioState *aio_get_linux_aio(AioContext *ctx)
+{
+    if (!ctx->linux_aio) {
+        ctx->linux_aio = laio_init();
+        laio_attach_aio_context(ctx->linux_aio, ctx);
+    }
+    return ctx->linux_aio;
+}
+#endif
+
+void aio_notify(AioContext *ctx)
+{
+    /* Write e.g. bh->scheduled before reading ctx->notify_me.  Pairs
+     * with atomic_or in aio_ctx_prepare or atomic_add in aio_poll.
+     */
+    smp_mb();
+    if (ctx->notify_me) {
+        event_notifier_set(&ctx->notifier);
+        atomic_mb_set(&ctx->notified, true);
+    }
+}
+
+void aio_notify_accept(AioContext *ctx)
+{
+    if (atomic_xchg(&ctx->notified, false)) {
+        event_notifier_test_and_clear(&ctx->notifier);
+    }
+}
+
+static void aio_timerlist_notify(void *opaque)
+{
+    aio_notify(opaque);
+}
+
+static void event_notifier_dummy_cb(EventNotifier *e)
+{
+}
+
+/* Returns true if aio_notify() was called (e.g. a BH was scheduled) */
+static bool event_notifier_poll(void *opaque)
+{
+    EventNotifier *e = opaque;
+    AioContext *ctx = container_of(e, AioContext, notifier);
+
+    return atomic_read(&ctx->notified);
+}
+
+AioContext *aio_context_new(Error **errp)
+{
+    int ret;
+    AioContext *ctx;
+
+    ctx = (AioContext *) g_source_new(&aio_source_funcs, sizeof(AioContext));
+    aio_context_setup(ctx);
+
+    ret = event_notifier_init(&ctx->notifier, false);
+    if (ret < 0) {
+        error_setg_errno(errp, -ret, "Failed to initialize event notifier");
+        goto fail;
+    }
+    g_source_set_can_recurse(&ctx->source, true);
+    qemu_lockcnt_init(&ctx->list_lock);
+    aio_set_event_notifier(ctx, &ctx->notifier,
+                           false,
+                           (EventNotifierHandler *)
+                           event_notifier_dummy_cb,
+                           event_notifier_poll);
+#ifdef CONFIG_LINUX_AIO
+    ctx->linux_aio = NULL;
+#endif
+    ctx->thread_pool = NULL;
+    qemu_rec_mutex_init(&ctx->lock);
+    timerlistgroup_init(&ctx->tlg, aio_timerlist_notify, ctx);
+
+    ctx->poll_ns = 0;
+    ctx->poll_max_ns = 0;
+    ctx->poll_grow = 0;
+    ctx->poll_shrink = 0;
+
+    return ctx;
+fail:
+    g_source_destroy(&ctx->source);
+    return NULL;
+}
+
+void aio_context_ref(AioContext *ctx)
+{
+    g_source_ref(&ctx->source);
+}
+
+void aio_context_unref(AioContext *ctx)
+{
+    g_source_unref(&ctx->source);
+}
+
+void aio_context_acquire(AioContext *ctx)
+{
+    qemu_rec_mutex_lock(&ctx->lock);
+}
+
+void aio_context_release(AioContext *ctx)
+{
+    qemu_rec_mutex_unlock(&ctx->lock);
+}