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

Block pull request

# gpg: Signature made Fri 06 Jun 2014 17:08:50 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: (42 commits)
  qapi: Extract qapi/block.json definitions
  qapi: Extract qapi/block-core.json definitions
  qapi: create two block related json modules
  qapi: Extract qapi/common.json definitions
  sheepdog: reload only header in a case of live snapshot
  sheepdog: fix vdi object update after live snapshot
  rbd: Fix leaks in rbd_start_aio() error path
  qemu-img: Document check exit codes
  block: fix wrong order in live block migration setup
  blockdev: acquire AioContext in block_set_io_throttle
  throttle: add detach/attach test case
  throttle: add throttle_detach/attach_aio_context()
  dataplane: Support VIRTIO_BLK_T_SCSI_CMD
  virtio-blk: Factor out virtio_blk_handle_scsi_req from virtio_blk_handle_scsi
  virtio-blk: Allow config-wce in dataplane
  block: Move declaration of bdrv_get_aio_context to block.h
  raw-posix: drop raw_get_aio_fd() since it is no longer used
  dataplane: implement async flush
  dataplane: delete IOQueue since it is no longer used
  dataplane: use the QEMU block layer for I/O
  ...

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

1 files changed, 10 insertions, 4 deletions

diff --git a/async.c b/async.c
index 6930185e64..5b6fe6b4cc 100644
--- a/async.c
+++ b/async.c
@@ -117,15 +117,21 @@ void qemu_bh_schedule_idle(QEMUBH *bh)
 
 void qemu_bh_schedule(QEMUBH *bh)
 {
+    AioContext *ctx;
+
     if (bh->scheduled)
         return;
+    ctx = bh->ctx;
     bh->idle = 0;
-    /* Make sure that idle & any writes needed by the callback are done
-     * before the locations are read in the aio_bh_poll.
+    /* Make 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.
      */
-    smp_wmb();
+    smp_mb();
     bh->scheduled = 1;
-    aio_notify(bh->ctx);
+    aio_notify(ctx);
 }