svn commit: r302130 - head/sys/vm

[Konstantin Belousov]

Author: kib
Date: Thu Jun 23 08:27:38 2016
New Revision: 302130
URL: https://svnweb.freebsd.org/changeset/base/302130

Log:
  Add a comment noting locking regime for vm_page_xunbusy().
  
  Reviewed by:	alc
  Sponsored by:	The FreeBSD Foundation
  MFC after:	2 weeks
  Approved by:	re (gjb)

Modified:
  head/sys/vm/vm_page.h

Modified: head/sys/vm/vm_page.h
==============================================================================
--- head/sys/vm/vm_page.h	Thu Jun 23 08:26:07 2016	(r302129)
+++ head/sys/vm/vm_page.h	Thu Jun 23 08:27:38 2016	(r302130)
@@ -552,6 +552,7 @@ void vm_page_lock_assert_KBI(vm_page_t m
 		    (m));						\
 } while (0)
 
+/* Note: page m's lock must not be owned by the caller. */
 #define	vm_page_xunbusy(m) do {						\
 	if (!atomic_cmpset_rel_int(&(m)->busy_lock,			\
 	    VPB_SINGLE_EXCLUSIVER, VPB_UNBUSIED))			\