From fefab489c71884fbf681ebcf7b17852998f1db7c Mon Sep 17 00:00:00 2001
From: Mark Andrews <marka@isc.org>
Date: Fri, 16 Nov 2001 11:04:38 +0000
Subject: [PATCH] pullup: 1129.   [bug]           Multithreaded servers could
 crash under heavy                         resolution load due to a race
 condition. [RT #2018]

---
 CHANGES         |  3 +++
 lib/dns/rbtdb.c | 19 ++++---------------
 2 files changed, 7 insertions(+), 15 deletions(-)

diff --git a/CHANGES b/CHANGES
index 412eb5ab5c..32d85fecd5 100644
--- a/CHANGES
+++ b/CHANGES
@@ -1,3 +1,6 @@
+1129.	[bug]		Multithreaded servers could crash under heavy
+			resolution load due to a race condition. [RT #2018]
+
 1126.	[bug]		The server could access a freed event if shut
 			down while a client start event was pending
 			delivery. [RT #2061]
diff --git a/lib/dns/rbtdb.c b/lib/dns/rbtdb.c
index bc2e540b29..97a145b166 100644
--- a/lib/dns/rbtdb.c
+++ b/lib/dns/rbtdb.c
@@ -15,7 +15,7 @@
  * WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  */
 
-/* $Id: rbtdb.c,v 1.168 2001/08/27 03:58:44 marka Exp $ */
+/* $Id: rbtdb.c,v 1.168.2.1 2001/11/16 11:04:38 marka Exp $ */
 
 /*
  * Principal Author: Bob Halley
@@ -746,7 +746,6 @@ no_references(dns_rbtdb_t *rbtdb, dns_rbtnode_t *node,
 {
 	isc_result_t result;
 	isc_boolean_t write_locked;
-	isc_boolean_t reacquire;
 	unsigned int locknum;
 
 	/*
@@ -786,15 +785,12 @@ no_references(dns_rbtdb_t *rbtdb, dns_rbtnode_t *node,
 	/*
 	 * XXXDCL need to add a deferred delete method for ISC_R_LOCKBUSY.
 	 */
-	reacquire = ISC_FALSE;
 	if (lock != isc_rwlocktype_write) {
 		/*
-		 * Free the node lock before acquiring a tree write lock, per
-		 * the lock hierarchy rules stated at the start of this file.
+		 * Locking hierarchy notwithstanding, we don't need to free
+		 * the node lock before acquiring the tree write lock because
+		 * we only do a trylock.
 		 */
-		UNLOCK(&rbtdb->node_locks[locknum].lock);
-		reacquire = ISC_TRUE;
-
 		if (lock == isc_rwlocktype_read)
 			RWUNLOCK(&rbtdb->tree_lock, isc_rwlocktype_read);
 
@@ -804,7 +800,6 @@ no_references(dns_rbtdb_t *rbtdb, dns_rbtnode_t *node,
 			      result == ISC_R_LOCKBUSY);
  
 		write_locked = ISC_TF(result == ISC_R_SUCCESS);
-
 	} else
 		write_locked = ISC_TRUE;
 
@@ -837,12 +832,6 @@ no_references(dns_rbtdb_t *rbtdb, dns_rbtnode_t *node,
 
 	if (lock == isc_rwlocktype_read)
 		RWLOCK(&rbtdb->tree_lock, isc_rwlocktype_read);
-
-	/*
-	 * Reacquire the node lock that the caller held if necessary.
-	 */
-	if (reacquire)
-		LOCK(&rbtdb->node_locks[locknum].lock);
 }
 
 static inline void