Author: rfm
Date: Tue Jun 9 19:31:09 2015
New Revision: 38607
URL: http://svn.gna.org/viewcvs/gnustep?rev=38607&view=rev
Log:
add comment
Modified:
libs/sqlclient/trunk/SQLClient.m
Modified: libs/sqlclient/trunk/SQLClient.m
URL:
http://svn.gna.org/viewcvs/gnustep/libs/sqlclient/trunk/SQLClient.m?rev=38607&r1=38606&r2=38607&view=diff
==============================================================================
--- libs/sqlclient/trunk/SQLClient.m (original)
+++ libs/sqlclient/trunk/SQLClient.m Tue Jun 9 19:31:09 2015
@@ -723,13 +723,23 @@
@end
-/**
- * Container for all instances.
+/* Containers for all instances.
+ * Access to and update of these containers is protected by classLock.
+ * Most other operations involving an instance are protected by a lock
+ * in that instance.
+ * To avoid deadlocks, we always obtain the instance lock *before* we
+ * obtain the class lock, so we don't get the situation where one thread
+ * has locked the instance and another has locked the class lock, and
+ * each thread then tries to get the other lock.
*/
-static NSRecursiveLock *cacheLock = nil;
static NSHashTable *clientsHash = 0;
static NSMapTable *clientsMap = 0;
static NSRecursiveLock *clientsLock = nil;
+
+/* Protect changes to the cache used for queries by any individual client.
+ */
+static NSRecursiveLock *cacheLock = nil;
+
static NSString *beginString = @"begin";
static NSArray *beginStatement = nil;
static NSString *commitString = @"commit";
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