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From: Konstantin Belousov <kib@FreeBSD.org>
Date: Sun, 3 Jul 2016 01:56:49 +0000 (UTC)
To: src-committers@freebsd.org, svn-src-all@freebsd.org,
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Subject: svn commit: r302322 - head/sys/kern
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Author: kib
Date: Sun Jul  3 01:56:48 2016
New Revision: 302322
URL: https://svnweb.freebsd.org/changeset/base/302322

Log:
  Remove racy assert. The thread which changes vnode usecount from 0 to 1
  does it under the vnode interlock, but the interlock is not owned by the
  asserting thread.  As result, we might read increased use counter but also
  still see VI_OWEINACT.
  
  In collaboration with: nwhitehorn
  Hardware donated by: IBM LTC
  Sponsored by:	The FreeBSD Foundation (kib)
  Approved by:	re (gjb)

Modified:
  head/sys/kern/vfs_subr.c

Modified: head/sys/kern/vfs_subr.c
==============================================================================
--- head/sys/kern/vfs_subr.c	Sun Jul  3 01:35:27 2016	(r302321)
+++ head/sys/kern/vfs_subr.c	Sun Jul  3 01:56:48 2016	(r302322)
@@ -2536,11 +2536,8 @@ vget(struct vnode *vp, int flags, struct
 	 *
 	 * Upgrade our holdcnt to a usecount.
 	 */
-	if (vp->v_type != VCHR &&
-	    vfs_refcount_acquire_if_not_zero(&vp->v_usecount)) {
-		VNASSERT((vp->v_iflag & VI_OWEINACT) == 0, vp,
-		    ("vnode with usecount and VI_OWEINACT set"));
-	} else {
+	if (vp->v_type == VCHR ||
+	    !vfs_refcount_acquire_if_not_zero(&vp->v_usecount)) {
 		VI_LOCK(vp);
 		if ((vp->v_iflag & VI_OWEINACT) == 0) {
 			oweinact = 0;