thread-pool: clean up thread_pool_completion_bh()

This patch simplifies thread_pool_completion_bh().

The function first checks elem->state:

  if (elem->state != THREAD_DONE) {
      continue;
  }

It then goes on to check elem->state == THREAD_DONE although we already
know this must be the case.

The QLIST_REMOVE() is duplicated down both branches of an if-else
statement so that can be lifted out as well.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Message-id: 1427992762-10126-1-git-send-email-stefanha@redhat.com
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

thread-pool.c

@@ -170,12 +170,12 @@ restart:
         if (elem->state != THREAD_DONE) {
             continue;
         }
-        if (elem->state == THREAD_DONE) {
-            trace_thread_pool_complete(pool, elem, elem->common.opaque,
-                                       elem->ret);
-        }
-        if (elem->state == THREAD_DONE && elem->common.cb) {
-            QLIST_REMOVE(elem, all);
+
+        trace_thread_pool_complete(pool, elem, elem->common.opaque,
+                                   elem->ret);
+        QLIST_REMOVE(elem, all);
+
+        if (elem->common.cb) {
             /* Read state before ret.  */
             smp_rmb();
 
@@ -188,8 +188,6 @@ restart:
             qemu_aio_unref(elem);
             goto restart;
         } else {
-            /* remove the request */
-            QLIST_REMOVE(elem, all);
             qemu_aio_unref(elem);
         }
     }