export pid symbols needed for kvm_vcpu_on_spin

Export the symbols required for a race-free kvm_vcpu_on_spin.

Signed-off-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
diff --git a/kernel/fork.c b/kernel/fork.c
index 25e4291..05b92c4 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -193,6 +193,7 @@
 	if (!profile_handoff_task(tsk))
 		free_task(tsk);
 }
+EXPORT_SYMBOL_GPL(__put_task_struct);
 
 /*
  * macro override instead of weak attribute alias, to workaround