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

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

Pull request

v2:
 * v1 emails 2/3 and 3/3 weren't sent due to an email failure
 * Included Sergio's updated wording in the commit description

# gpg: Signature made Wed 08 Nov 2017 19:12:01 GMT
# gpg:                using RSA key 0x9CA4ABB381AB73C8
# gpg: Good signature from "Stefan Hajnoczi <stefanha@redhat.com>"
# gpg:                 aka "Stefan Hajnoczi <stefanha@gmail.com>"
# Primary key fingerprint: 8695 A8BF D3F9 7CDA AC35  775A 9CA4 ABB3 81AB 73C8

* remotes/stefanha/tags/block-pull-request:
  util/async: use atomic_mb_set in qemu_bh_cancel
  tests-aio-multithread: fix /aio/multi/schedule race condition

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