Revert "Remove gencache_[un]lock_entry"

This reverts commit 7a5a575ffe5196caecedc93970a25abfbe6f8059.
(This used to be commit 62e444dd50ae974c2ab9a553cdf7f188a8f2c538)

3 files changed, 37 insertions, 2 deletions

diff --git a/source3/include/proto.h b/source3/include/proto.h
index 278a42a974..9958c91dca 100644
--- a/source3/include/proto.h
+++ b/source3/include/proto.h
@@ -606,6 +606,8 @@ bool gencache_get_data_blob(const char *keystr, DATA_BLOB *blob, bool *expired);
 bool gencache_set_data_blob(const char *keystr, const DATA_BLOB *blob, time_t timeout);
 void gencache_iterate(void (*fn)(const char* key, const char *value, time_t timeout, void* dptr),
                       void* data, const char* keystr_pattern);
+int gencache_lock_entry( const char *key );
+void gencache_unlock_entry( const char *key );
 
 /* The following definitions come from lib/genrand.c  */
 
diff --git a/source3/lib/gencache.c b/source3/lib/gencache.c
index a55b2ab9ba..1b4342a62b 100644
--- a/source3/lib/gencache.c
+++ b/source3/lib/gencache.c
@@ -484,3 +484,28 @@ void gencache_iterate(void (*fn)(const char* key, const char *value, time_t time
 	
 	tdb_search_list_free(first_node);
 }
+
+/********************************************************************
+ lock a key
+********************************************************************/
+
+int gencache_lock_entry( const char *key )
+{
+	if (!gencache_init())
+		return -1;
+	
+	return tdb_lock_bystring(cache, key);
+}
+
+/********************************************************************
+ unlock a key
+********************************************************************/
+
+void gencache_unlock_entry( const char *key )
+{
+	if (!gencache_init())
+		return;
+	
+	tdb_unlock_bystring(cache, key);
+	return;
+}
diff --git a/source3/libsmb/dsgetdcname.c b/source3/libsmb/dsgetdcname.c
index afc87030d0..2a445cbd5a 100644
--- a/source3/libsmb/dsgetdcname.c
+++ b/source3/libsmb/dsgetdcname.c
@@ -159,6 +159,7 @@ static NTSTATUS dsgetdcname_cache_store(TALLOC_CTX *mem_ctx,
 {
 	time_t expire_time;
 	char *key;
+	bool ret = false;
 
 	if (!gencache_init()) {
 		return NT_STATUS_INTERNAL_DB_ERROR;
@@ -171,8 +172,15 @@ static NTSTATUS dsgetdcname_cache_store(TALLOC_CTX *mem_ctx,
 
 	expire_time = time(NULL) + DSGETDCNAME_CACHE_TTL;
 
-	return gencache_set_data_blob(key, blob, expire_time)
-		? NT_STATUS_OK : NT_STATUS_UNSUCCESSFUL;
+	if (gencache_lock_entry(key) != 0) {
+		return NT_STATUS_LOCK_NOT_GRANTED;
+	}
+
+	ret = gencache_set_data_blob(key, blob, expire_time);
+
+	gencache_unlock_entry(key);
+
+	return ret ? NT_STATUS_OK : NT_STATUS_UNSUCCESSFUL;
 }
 
 /****************************************************************