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

Pull request

v2:
 * Dropped Fam's git-publish series because there is still ongoing discussion

# gpg: Signature made Thu 15 Feb 2018 09:42:03 GMT
# gpg:                using RSA key 9CA4ABB381AB73C8
# 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:
  misc: fix spelling
  ratelimit: don't align wait time with slices
  vl: pause vcpus before stopping iothreads

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

1 files changed, 9 insertions, 1 deletions

diff --git a/vl.c b/vl.c
index 21878496ec..7a5554bc41 100644
--- a/vl.c
+++ b/vl.c
@@ -4767,10 +4767,18 @@ int main(int argc, char **argv, char **envp)
 
     main_loop();
     replay_disable_events();
-    iothread_stop_all();
 
+    /* The ordering of the following is delicate.  Stop vcpus to prevent new
+     * I/O requests being queued by the guest.  Then stop IOThreads (this
+     * includes a drain operation and completes all request processing).  At
+     * this point emulated devices are still associated with their IOThreads
+     * (if any) but no longer have any work to do.  Only then can we close
+     * block devices safely because we know there is no more I/O coming.
+     */
     pause_all_vcpus();
+    iothread_stop_all();
     bdrv_close_all();
+
     res_free();
 
     /* vhost-user must be cleaned up before chardevs.  */