svn commit: r184651 - head/sys/ufs/ufs

[John Baldwin]

Author: jhb
Date: Tue Nov  4 18:56:12 2008
New Revision: 184651
URL: http://svn.freebsd.org/changeset/base/184651

Log:
  Quiet a WITNESS warning with the dirhash sx locks by setting the DUPOK
  flag.  Specifically, if two threads race to create a dirhash for a
  directory, then one might already have created a private dirhash
  structure (and locked it) when it realizes the directory now has a
  structure and tries to lock that one.

Modified:
  head/sys/ufs/ufs/ufs_dirhash.c

Modified: head/sys/ufs/ufs/ufs_dirhash.c
==============================================================================
--- head/sys/ufs/ufs/ufs_dirhash.c	Tue Nov  4 18:54:44 2008	(r184650)
+++ head/sys/ufs/ufs/ufs_dirhash.c	Tue Nov  4 18:56:12 2008	(r184651)
@@ -181,7 +181,16 @@ ufsdirhash_create(struct inode *ip)
 			if (ndh == NULL)
 				return (NULL);
 			refcount_init(&ndh->dh_refcount, 1);
-			sx_init(&ndh->dh_lock, "dirhash");
+
+			/*
+			 * The DUPOK is to prevent warnings from the
+			 * sx_slock() a few lines down which is safe
+			 * since the duplicate lock in that case is
+			 * the one for this dirhash we are creating
+			 * now which has no external references until
+			 * after this function returns.
+			 */
+			sx_init_flags(&ndh->dh_lock, "dirhash", SX_DUPOK);
 			sx_xlock(&ndh->dh_lock);
 		}
 		/*