Fix for bug 39484 after review. I inserted the review results (also including the patches itself):

"Release_lock("hello")" is now also successful when delivering NULL, replaced two sleeps by wait_condition. The last two "sleep 1" have not been replaced as all tried wait conditions leaded to nondeterministic results, especially to succeeding concurrent updates. To replace the sleeps there should be some time planned (or internal knowledge of the server may help).
 

mysql-test/include/concurrent.inc

@@ -11,6 +11,11 @@
 #   $engine_type                     storage engine to be tested
 #
 # Last update:
+# 2009-02-13 HH "Release_lock("hello")" is now also successful when delivering NULL,
+#               replaced two sleeps by wait_condition. The last two "sleep 1" have not been
+#               replaced as all tried wait conditions leaded to nondeterministic results, especially
+#               to succeeding concurrent updates. To replace the sleeps there should be some time
+#               planned (or internal knowledge of the server may help).
 # 2006-08-02 ML test refactored
 #               old name was t/innodb_concurrent.test
 #               main code went into include/concurrent.inc
@@ -21,7 +26,6 @@
 #
 
 connection default;
-
 #
 # Show prerequisites for this test.
 #
@@ -50,8 +54,6 @@ GRANT USAGE ON test.* TO mysqltest@localhost;
 #
 # Preparatory cleanup.
 #
-DO release_lock("hello");
-DO release_lock("hello2");
 --disable_warnings
 drop table if exists t1;
 --enable_warnings
@@ -86,13 +88,14 @@ drop table if exists t1;
       connection thread2;
       --echo ** Start transaction for thread 2
       begin;
-      --echo ** Update will cause a table scan and a new ULL  will 
+      --echo ** Update will cause a table scan and a new ULL  will
       --echo ** be created and blocked on the first row where tipo=11.
       send update t1 set eta=1+get_lock("hello",10)*0 where tipo=11;
-      sleep 1;
 
   --echo ** connection thread1
   connection thread1;
+  let $wait_condition= select count(*)= 1 from information_schema.processlist where state= 'User lock';
+  --source include/wait_condition.inc
   --echo ** Start new transaction for thread 1
   begin;
   --echo ** Update on t1 will cause a table scan which will be blocked because
@@ -111,7 +114,9 @@ drop table if exists t1;
   }
   --echo ** Release user level name lock from thread 1. This will cause the ULL
   --echo ** on thread 2 to end its wait.
-  select release_lock("hello");
+# Due to Bug#32782 User lock hash fails to find lock, which probably also cause Bug#39484 (main.concurrent_innodb_safelog fails sporadically) the success of the following
+# is also guaranteed for NULL. Replaced SELECT by DO (no result).
+  DO release_lock("hello");
   --echo ** Table is now updated with a new eta on tipo=22 for thread 1.
   select * from t1;
 
@@ -119,7 +124,9 @@ drop table if exists t1;
       connection thread2;
       --echo ** Release the lock and collect result from update on thread 2
       reap;
-      select release_lock("hello");
+# Due to Bug#32782 User lock hash fails to find lock, which probably also cause Bug#39484 (main.concurrent_innodb_safelog fails sporadically) the success of the following
+# is also guaranteed for NULL. Replaced SELECT by DO (no result).
+      DO release_lock("hello");
       --echo ** Table should have eta updates where tipo=11 but updates made by
       --echo ** thread 1 shouldn't be visible yet.
       select * from t1;
@@ -183,10 +190,11 @@ drop table t1;
       --echo ** This will cause a hang on the first row where tipo=1 until the
       --echo ** blocking ULL is released.
       send update t1 set eta=1+get_lock("hello",10)*0 where tipo=1;
-      sleep 1;
 
-  --echo ** connection thread1
+--echo ** connection thread1
   connection thread1;
+  let $wait_condition= select count(*)= 1 from information_schema.processlist where state= 'User lock';
+  --source include/wait_condition.inc
   --echo ** Start transaction on thread 1
   begin;
   --echo ** Update on t1 will cause a table scan which will be blocked because
@@ -204,7 +212,9 @@ drop table t1;
     update t1 set tipo=1 where tipo=2;
   }
   --echo ** Release ULL. This will release the next waiting ULL on thread 2.
-  select release_lock("hello");
+# Due to Bug#32782 User lock hash fails to find lock, which probably also cause Bug#39484 (main.concurrent_innodb_safelog fails sporadically)the success of the following
+# is also guaranteed for NULL. Replaced SELECT by DO (no result).
+  DO release_lock("hello");
   --echo ** The table should still be updated with updates for thread 1 only:
   select * from t1;
 
@@ -212,7 +222,9 @@ drop table t1;
       connection thread2;
       --echo ** Release the lock and collect result from thread 2:
       reap;
-      select release_lock("hello");
+# Due to Bug#32782 User lock hash fails to find lock, which probably also cause Bug#39484 (main.concurrent_innodb_safelog fails sporadically) the success of the following
+# is also guaranteed for NULL. Replaced SELECT by DO (no result).
+      DO release_lock("hello");
       --echo ** Seen from thread 2 the table should have been updated on four
       --echo ** places.
       select * from t1;
@@ -264,15 +276,18 @@ drop table t1;
       --echo ** Update will create a table scan which creates a ULL where a=2;
       --echo ** this will hang waiting on thread 1.
       send update t1 set b=10+get_lock(concat("hello",a),10)*0 where a=2;
-      sleep 1;
 
   --echo ** connection thread1
   connection thread1;
+  let $wait_condition= select count(*)= 1 from information_schema.processlist where state= 'User lock';
+  --source include/wait_condition.inc
   --echo ** Insert new values to t1 from thread 1; this created an implicit
   --echo ** commit since there are no on-going transactions.
   insert into t1 values (1,1);
   --echo ** Release the ULL (thread 2 updates will finish).
-  select release_lock("hello2");
+# Due to Bug#32782 User lock hash fails to find lock, which probably also cause Bug#39484 (main.concurrent_innodb_safelog fails sporadically) the success of the following
+# is also guaranteed for NULL. Replaced SELECT by DO (no result).
+  DO release_lock("hello2");
   --echo ** ..but thread 1 will still see t1 as if nothing has happend:
   select * from t1;
 
@@ -280,7 +295,9 @@ drop table t1;
       connection thread2;
       --echo ** Collect results from thread 2 and release the lock.
       reap;
-      select release_lock("hello2");
+# Due to Bug#32782 User lock hash fails to find lock, which probably also cause Bug#39484 (main.concurrent_innodb_safelog fails sporadically) the success of the following
+# is also guaranteed for NULL. Replaced SELECT by DO (no result).
+      DO release_lock("hello2");
       --echo ** The table should look like the original+updates for thread 2,
       --echo ** and consist of new rows:
       select * from t1;
@@ -534,6 +551,9 @@ drop table t1;
       connection thread2;
       begin;
       send delete from t1 where tipo=2;
+# The sleep has not been replaced as all tried wait conditions leaded to sporadically
+# succeding update in the following thread. Also the used status variables '%lock%' and
+# 'innodb_deleted_rows' and infos in processlist where not sucessful.
       sleep 1;
 
   --echo ** connection thread1
@@ -594,8 +614,11 @@ drop table t1;
       connection thread2;
       begin;
       send delete from t1 where tipo=2;
+# The sleep has not been replaced as all tried wait conditions leaded to sporadically
+# succeding update in the following thread. Also the used status variables '%lock%' and
+# 'innodb_deleted_rows' and infos in processlist where not sucessful.
       sleep 1;
-  
+ 
   --echo ** connection thread1
   connection thread1;
   begin;

mysql-test/r/concurrent_innodb_safelog.result

@@ -7,8 +7,6 @@ SELECT @@global.innodb_locks_unsafe_for_binlog;
 0
 # keep_locks == 1
 GRANT USAGE ON test.* TO mysqltest@localhost;
-DO release_lock("hello");
-DO release_lock("hello2");
 drop table if exists t1;
 
 **
@@ -36,7 +34,7 @@ get_lock("hello",10)
 ** connection thread2
 ** Start transaction for thread 2
 begin;
-** Update will cause a table scan and a new ULL  will 
+** Update will cause a table scan and a new ULL  will
 ** be created and blocked on the first row where tipo=11.
 update t1 set eta=1+get_lock("hello",10)*0 where tipo=11;
 ** connection thread1
@@ -51,9 +49,7 @@ update t1 set eta=2 where tipo=22;
 ERROR HY000: Lock wait timeout exceeded; try restarting transaction
 ** Release user level name lock from thread 1. This will cause the ULL
 ** on thread 2 to end its wait.
-select release_lock("hello");
-release_lock("hello")
-1
+DO release_lock("hello");
 ** Table is now updated with a new eta on tipo=22 for thread 1.
 select * from t1;
 eta	tipo	c
@@ -70,9 +66,7 @@ eta	tipo	c
 90	11	kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk
 ** connection thread2
 ** Release the lock and collect result from update on thread 2
-select release_lock("hello");
-release_lock("hello")
-1
+DO release_lock("hello");
 ** Table should have eta updates where tipo=11 but updates made by
 ** thread 1 shouldn't be visible yet.
 select * from t1;
@@ -194,9 +188,7 @@ begin;
 update t1 set tipo=1 where tipo=2;
 ERROR HY000: Lock wait timeout exceeded; try restarting transaction
 ** Release ULL. This will release the next waiting ULL on thread 2.
-select release_lock("hello");
-release_lock("hello")
-1
+DO release_lock("hello");
 ** The table should still be updated with updates for thread 1 only:
 select * from t1;
 eta	tipo	c
@@ -213,9 +205,7 @@ eta	tipo	c
 90	11	kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk
 ** connection thread2
 ** Release the lock and collect result from thread 2:
-select release_lock("hello");
-release_lock("hello")
-1
+DO release_lock("hello");
 ** Seen from thread 2 the table should have been updated on four
 ** places.
 select * from t1;
@@ -319,9 +309,7 @@ update t1 set b=10+get_lock(concat("hello",a),10)*0 where a=2;
 ** commit since there are no on-going transactions.
 insert into t1 values (1,1);
 ** Release the ULL (thread 2 updates will finish).
-select release_lock("hello2");
-release_lock("hello2")
-1
+DO release_lock("hello2");
 ** ..but thread 1 will still see t1 as if nothing has happend:
 select * from t1;
 a	b
@@ -332,9 +320,7 @@ a	b
 1	1
 ** connection thread2
 ** Collect results from thread 2 and release the lock.
-select release_lock("hello2");
-release_lock("hello2")
-1
+DO release_lock("hello2");
 ** The table should look like the original+updates for thread 2,
 ** and consist of new rows:
 select * from t1;

mysql-test/r/concurrent_innodb_unsafelog.result

@@ -7,8 +7,6 @@ SELECT @@global.innodb_locks_unsafe_for_binlog;
 1
 # keep_locks == 0
 GRANT USAGE ON test.* TO mysqltest@localhost;
-DO release_lock("hello");
-DO release_lock("hello2");
 drop table if exists t1;
 
 **
@@ -36,7 +34,7 @@ get_lock("hello",10)
 ** connection thread2
 ** Start transaction for thread 2
 begin;
-** Update will cause a table scan and a new ULL  will 
+** Update will cause a table scan and a new ULL  will
 ** be created and blocked on the first row where tipo=11.
 update t1 set eta=1+get_lock("hello",10)*0 where tipo=11;
 ** connection thread1
@@ -50,9 +48,7 @@ begin;
 update t1 set eta=2 where tipo=22;
 ** Release user level name lock from thread 1. This will cause the ULL
 ** on thread 2 to end its wait.
-select release_lock("hello");
-release_lock("hello")
-1
+DO release_lock("hello");
 ** Table is now updated with a new eta on tipo=22 for thread 1.
 select * from t1;
 eta	tipo	c
@@ -69,9 +65,7 @@ eta	tipo	c
 90	11	kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk
 ** connection thread2
 ** Release the lock and collect result from update on thread 2
-select release_lock("hello");
-release_lock("hello")
-1
+DO release_lock("hello");
 ** Table should have eta updates where tipo=11 but updates made by
 ** thread 1 shouldn't be visible yet.
 select * from t1;
@@ -192,9 +186,7 @@ begin;
 ** do not match the WHERE condition are released.
 update t1 set tipo=1 where tipo=2;
 ** Release ULL. This will release the next waiting ULL on thread 2.
-select release_lock("hello");
-release_lock("hello")
-1
+DO release_lock("hello");
 ** The table should still be updated with updates for thread 1 only:
 select * from t1;
 eta	tipo	c
@@ -211,9 +203,7 @@ eta	tipo	c
 90	11	kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk
 ** connection thread2
 ** Release the lock and collect result from thread 2:
-select release_lock("hello");
-release_lock("hello")
-1
+DO release_lock("hello");
 ** Seen from thread 2 the table should have been updated on four
 ** places.
 select * from t1;
@@ -317,9 +307,7 @@ update t1 set b=10+get_lock(concat("hello",a),10)*0 where a=2;
 ** commit since there are no on-going transactions.
 insert into t1 values (1,1);
 ** Release the ULL (thread 2 updates will finish).
-select release_lock("hello2");
-release_lock("hello2")
-1
+DO release_lock("hello2");
 ** ..but thread 1 will still see t1 as if nothing has happend:
 select * from t1;
 a	b
@@ -330,9 +318,7 @@ a	b
 1	1
 ** connection thread2
 ** Collect results from thread 2 and release the lock.
-select release_lock("hello2");
-release_lock("hello2")
-1
+DO release_lock("hello2");
 ** The table should look like the original+updates for thread 2,
 ** and consist of new rows:
 select * from t1;