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From: Konstantin Belousov <kib@FreeBSD.org>
Date: Mon, 3 Nov 2008 14:11:06 +0000 (UTC)
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Subject: svn commit: r184591 - in stable/7/sys: . kern
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Author: kib
Date: Mon Nov  3 14:11:06 2008
New Revision: 184591
URL: http://svn.freebsd.org/changeset/base/184591

Log:
  In vfs_busy(), lockmgr() cannot legitimately sleep, because code checked
  MNTK_UNMOUNT before, and mnt_mtx is used as interlock. vfs_busy() always
  tries to obtain a shared lock on mnt_lock, the other user is unmount who
  tries to drain it, setting MNTK_UNMOUNT before.
  
  Approved by:	re (kensmith)

Modified:
  stable/7/sys/   (props changed)
  stable/7/sys/kern/vfs_subr.c

Modified: stable/7/sys/kern/vfs_subr.c
==============================================================================
--- stable/7/sys/kern/vfs_subr.c	Mon Nov  3 14:08:08 2008	(r184590)
+++ stable/7/sys/kern/vfs_subr.c	Mon Nov  3 14:11:06 2008	(r184591)
@@ -361,7 +361,7 @@ vfs_busy(struct mount *mp, int flags, st
 	}
 	if (interlkp)
 		mtx_unlock(interlkp);
-	lkflags = LK_SHARED | LK_INTERLOCK;
+	lkflags = LK_SHARED | LK_INTERLOCK | LK_NOWAIT;
 	if (lockmgr(&mp->mnt_lock, lkflags, MNT_MTX(mp), td))
 		panic("vfs_busy: unexpected lock failure");
 	return (0);