From: Stefan Hajnoczi <stefanha@redhat.com>

Calling aio_poll() directly may have been fine previously, but this is
the future, man!  The difference between an aio_poll() loop and
BDRV_POLL_WHILE() is that BDRV_POLL_WHILE() releases the AioContext
around aio_poll().

This allows the IOThread to run fd handlers or BHs to complete the
request.  Failure to release the AioContext causes deadlocks.

Using BDRV_POLL_WHILE() partially fixes a 'savevm' hang with -object
iothread.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 block/io.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/block/io.c b/block/io.c
index 684ea46..e158ae0 100644
--- a/block/io.c
+++ b/block/io.c
@@ -2023,9 +2023,7 @@ bdrv_rw_vmstate(BlockDriverState *bs, QEMUIOVector *qiov, int64_t pos,
         Coroutine *co = qemu_coroutine_create(bdrv_co_rw_vmstate_entry, &data);
 
         bdrv_coroutine_enter(bs, co);
-        while (data.ret == -EINPROGRESS) {
-            aio_poll(bdrv_get_aio_context(bs), true);
-        }
+        BDRV_POLL_WHILE(bs, data.ret == -EINPROGRESS);
         return data.ret;
     }
 }
-- 
1.8.3.1