bottom halves: introduce bh call function

This patch introduces aio_bh_call function. It is used to execute
bottom halves as callbacks without adding them to the queue.

Signed-off-by: Pavel Dovgalyuk <pavel.dovgaluk@ispras.ru>
Message-Id: <20150917162450.8676.56980.stgit@PASHA-ISP.def.inno>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Pavel Dovgalyuk <Pavel.Dovgaluk@ispras.ru>
diff --git a/async.c b/async.c
index bdc64a3..9589e4b 100644
--- a/async.c
+++ b/async.c
@@ -59,6 +59,11 @@
     return bh;
 }
 
+void aio_bh_call(QEMUBH *bh)
+{
+    bh->cb(bh->opaque);
+}
+
 /* Multiple occurrences of aio_bh_poll cannot be called concurrently */
 int aio_bh_poll(AioContext *ctx)
 {
@@ -84,7 +89,7 @@
                 ret = 1;
             }
             bh->idle = 0;
-            bh->cb(bh->opaque);
+            aio_bh_call(bh);
         }
     }