During incoming postcopy, the destination qemu will invoke
qemu_rdma_wait_comp_channel in a seprate thread. So does not use rdma
yield, and poll the completion channel fd instead.

Signed-off-by: Lidong Chen <lidongchen@tencent.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
---
 migration/rdma.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/migration/rdma.c b/migration/rdma.c
index 854f355..ed9cfb1 100644
--- a/migration/rdma.c
+++ b/migration/rdma.c
@@ -1490,11 +1490,13 @@ static int qemu_rdma_wait_comp_channel(RDMAContext *rdma)
      * Coroutine doesn't start until migration_fd_process_incoming()
      * so don't yield unless we know we're running inside of a coroutine.
      */
-    if (rdma->migration_started_on_destination) {
+    if (rdma->migration_started_on_destination &&
+        migration_incoming_get_current()->state == MIGRATION_STATUS_ACTIVE) {
         yield_until_fd_readable(rdma->comp_channel->fd);
     } else {
         /* This is the source side, we're in a separate thread
          * or destination prior to migration_fd_process_incoming()
+         * after postcopy, the destination also in a seprate thread.
          * we can't yield; so we have to poll the fd.
          * But we need to be able to handle 'cancel' or an error
          * without hanging forever.
-- 
1.8.3.1