[6.0] 4f672b6e1 Add a note about concurrency in the VSC_Iter documentation.

[Dridi Boukelmoune]

commit 4f672b6e1f1fa5fe319d80a77b923a825517305f
Author: Geoff Simmons <geoff at uplex.de>
Date:   Mon Aug 20 10:03:56 2018 +0200

    Add a note about concurrency in the VSC_Iter documentation.

diff --git a/include/vapi/vsc.h b/include/vapi/vsc.h
index 82fa89fbd..3ae67290f 100644
--- a/include/vapi/vsc.h
+++ b/include/vapi/vsc.h
@@ -135,6 +135,10 @@ int VSC_Iter(struct vsc *, struct vsm *, VSC_iter_f *, void *priv);
 	 *
 	 * The returned points are valid until the next call to VSC_Iter()
 	 *
+	 * Not safe for concurrent reads with the same vsc and vsm
+	 * handles.  For concurrency, initalize and attach separate
+	 * structs vsc and vsm.
+	 *
 	 * Arguments:
 	 *	    vd: The vsm context
 	 *	  func: The callback function