Index: openacs-4/packages/acs-kernel/acs-kernel.info
===================================================================
RCS file: /usr/local/cvsroot/openacs-4/packages/acs-kernel/acs-kernel.info,v
diff -u -N -r1.135 -r1.136
--- openacs-4/packages/acs-kernel/acs-kernel.info	27 Jul 2015 12:29:28 -0000	1.135
+++ openacs-4/packages/acs-kernel/acs-kernel.info	27 Jul 2015 12:51:21 -0000	1.136
@@ -9,15 +9,15 @@
     <implements-subsite-p>f</implements-subsite-p>
     <inherit-templates-p>t</inherit-templates-p>
     
-    <version name="5.9.0d5" url="http://openacs.org/repository/download/apm/acs-kernel-5.9.0d5.apm">
+    <version name="5.9.0d6" url="http://openacs.org/repository/download/apm/acs-kernel-5.9.0d6.apm">
         <owner url="mailto:oct@openacs.org">OpenACS Core Team</owner>
         <summary>Routines and data models providing the foundation for OpenACS-based Web services.</summary>
         <release-date>2013-09-08</release-date>
         <vendor url="http://openacs.org">OpenACS</vendor>
         <description format="text/html">The OpenACS kernel contains the core datamodel create and drop scripts for such things as objects, groups, partiies and the supporting PL/SQL and PL/pgSQL procedures.</description>
         <maturity>3</maturity>
 
-        <provides url="acs-kernel" version="5.9.0d5"/>
+        <provides url="acs-kernel" version="5.9.0d6"/>
 
         <callbacks>
         </callbacks>
Index: openacs-4/packages/acs-kernel/sql/postgresql/acs-permissions-create.sql
===================================================================
RCS file: /usr/local/cvsroot/openacs-4/packages/acs-kernel/sql/postgresql/acs-permissions-create.sql,v
diff -u -N -r1.38 -r1.39
--- openacs-4/packages/acs-kernel/sql/postgresql/acs-permissions-create.sql	23 Apr 2013 15:23:11 -0000	1.38
+++ openacs-4/packages/acs-kernel/sql/postgresql/acs-permissions-create.sql	27 Jul 2015 12:51:21 -0000	1.39
@@ -504,31 +504,17 @@
    grant_permission__privilege varchar
 ) RETURNS integer AS $$
 DECLARE
-    exists_p                            boolean;
 BEGIN
-    lock table acs_permissions_lock;
-
-    select count(*) > 0 into exists_p
-      from acs_permissions
-     where object_id = grant_permission__object_id
-       and grantee_id = grant_permission__grantee_id
-       and privilege = grant_permission__privilege;
-
-    if not exists_p then
-
-        insert into acs_permissions
-          (object_id, grantee_id, privilege)
-          values
-          (grant_permission__object_id, grant_permission__grantee_id, 
-          grant_permission__privilege);
-
-    end if;
-
-    -- exception
-    --  when dup_val_on_index then
-    --    return;
-
-    return 0; 
+    insert into acs_permissions
+      (object_id, grantee_id, privilege)
+      values
+      (grant_permission__object_id, grant_permission__grantee_id, 
+      grant_permission__privilege);
+    
+    return 0;
+EXCEPTION 
+    when unique_violation then
+      return 0;
 END;
 $$ LANGUAGE plpgsql;
 
@@ -549,8 +535,6 @@
 ) RETURNS integer AS $$
 DECLARE
 BEGIN
-    lock table acs_permissions_lock;
-
     delete from acs_permissions
     where object_id = revoke_permission__object_id
     and grantee_id = revoke_permission__grantee_id
Index: openacs-4/packages/acs-kernel/sql/postgresql/upgrade/upgrade-5.9.0d5-5.9.0d6.sql
===================================================================
RCS file: /usr/local/cvsroot/openacs-4/packages/acs-kernel/sql/postgresql/upgrade/upgrade-5.9.0d5-5.9.0d6.sql,v
diff -u -N
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ openacs-4/packages/acs-kernel/sql/postgresql/upgrade/upgrade-5.9.0d5-5.9.0d6.sql	27 Jul 2015 12:51:21 -0000	1.1
@@ -0,0 +1,48 @@
+
+-- Antonio Pisano 2015-07-29: removed exclusive lock
+-- for this procedures as it is sufficient to handle
+-- exception/ignore the case. Locking esclusively
+-- could cause deadlock in certain situations.
+
+--
+-- procedure acs_permission__grant_permission/3
+--
+CREATE OR REPLACE FUNCTION acs_permission__grant_permission(
+   grant_permission__object_id integer,
+   grant_permission__grantee_id integer,
+   grant_permission__privilege varchar
+) RETURNS integer AS $$
+DECLARE
+BEGIN
+    insert into acs_permissions
+      (object_id, grantee_id, privilege)
+      values
+      (grant_permission__object_id, grant_permission__grantee_id, 
+      grant_permission__privilege);
+    
+    return 0;
+EXCEPTION 
+    when unique_violation then
+      return 0;
+END;
+$$ LANGUAGE plpgsql;
+
+
+--
+-- procedure acs_permission__revoke_permission/3
+--
+CREATE OR REPLACE FUNCTION acs_permission__revoke_permission(
+   revoke_permission__object_id integer,
+   revoke_permission__grantee_id integer,
+   revoke_permission__privilege varchar
+) RETURNS integer AS $$
+DECLARE
+BEGIN
+    delete from acs_permissions
+    where object_id = revoke_permission__object_id
+    and grantee_id = revoke_permission__grantee_id
+    and privilege = revoke_permission__privilege;
+
+    return 0; 
+END;
+$$ LANGUAGE plpgsql;