Merge remote-tracking branch 'remotes/stefanha/tags/block-pull-request' into staging

Pull request

These fixes make dataplane work again after the notify_me optimization was
added.  They also solve QEMUBH memory leaks and fix a bug in dataplane's
cleanup code.

# gpg: Signature made Wed Jul 29 14:50:26 2015 BST using RSA key ID 81AB73C8
# gpg: Good signature from "Stefan Hajnoczi <stefanha@redhat.com>"
# gpg:                 aka "Stefan Hajnoczi <stefanha@gmail.com>"

* remotes/stefanha/tags/block-pull-request:
  AioContext: force event loop iteration using BH
  AioContext: avoid leaking BHs on cleanup
  virtio-blk-dataplane: delete bottom half before the AioContext is freed

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

3 files changed, 31 insertions, 3 deletions

diff --git a/async.c b/async.c
index 9a98a74acb..efce14b63a 100644
--- a/async.c
+++ b/async.c
@@ -79,8 +79,10 @@ int aio_bh_poll(AioContext *ctx)
          * aio_notify again if necessary.
          */
         if (!bh->deleted && atomic_xchg(&bh->scheduled, 0)) {
-            if (!bh->idle)
+            /* Idle BHs and the notify BH don't count as progress */
+            if (!bh->idle && bh != ctx->notify_dummy_bh) {
                 ret = 1;
+            }
             bh->idle = 0;
             bh->cb(bh->opaque);
         }
@@ -230,7 +232,21 @@ aio_ctx_finalize(GSource     *source)
 {
     AioContext *ctx = (AioContext *) source;
 
+    qemu_bh_delete(ctx->notify_dummy_bh);
     thread_pool_free(ctx->thread_pool);
+
+    qemu_mutex_lock(&ctx->bh_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_mutex_unlock(&ctx->bh_lock);
+
     aio_set_event_notifier(ctx, &ctx->notifier, NULL);
     event_notifier_cleanup(&ctx->notifier);
     rfifolock_destroy(&ctx->lock);
@@ -285,8 +301,15 @@ static void aio_timerlist_notify(void *opaque)
 
 static void aio_rfifolock_cb(void *opaque)
 {
+    AioContext *ctx = opaque;
+
     /* Kick owner thread in case they are blocked in aio_poll() */
-    aio_notify(opaque);
+    qemu_bh_schedule(ctx->notify_dummy_bh);
+}
+
+static void notify_dummy_bh(void *opaque)
+{
+    /* Do nothing, we were invoked just to force the event loop to iterate */
 }
 
 static void event_notifier_dummy_cb(EventNotifier *e)
@@ -313,6 +336,8 @@ AioContext *aio_context_new(Error **errp)
     rfifolock_init(&ctx->lock, aio_rfifolock_cb, ctx);
     timerlistgroup_init(&ctx->tlg, aio_timerlist_notify, ctx);
 
+    ctx->notify_dummy_bh = aio_bh_new(ctx, notify_dummy_bh, NULL);
+
     return ctx;
 }
 
diff --git a/hw/block/dataplane/virtio-blk.c b/hw/block/dataplane/virtio-blk.c
index 3db139b8a4..6106e46158 100644
--- a/hw/block/dataplane/virtio-blk.c
+++ b/hw/block/dataplane/virtio-blk.c
@@ -223,8 +223,8 @@ void virtio_blk_data_plane_destroy(VirtIOBlockDataPlane *s)
     virtio_blk_data_plane_stop(s);
     blk_op_unblock_all(s->conf->conf.blk, s->blocker);
     error_free(s->blocker);
-    object_unref(OBJECT(s->iothread));
     qemu_bh_delete(s->bh);
+    object_unref(OBJECT(s->iothread));
     g_free(s);
 }
 
diff --git a/include/block/aio.h b/include/block/aio.h
index 9dd32e0f13..400b1b0020 100644
--- a/include/block/aio.h
+++ b/include/block/aio.h
@@ -114,6 +114,9 @@ struct AioContext {
     bool notified;
     EventNotifier notifier;
 
+    /* Scheduling this BH forces the event loop it iterate */
+    QEMUBH *notify_dummy_bh;
+
     /* Thread pool for performing work and receiving completion callbacks */
     struct ThreadPool *thread_pool;