[389-commits] [389-ds-base] branch 389-ds-base-1.3.10 updated: Issue 50745: ns-slapd hangs during CleanAllRUV tests

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mreynolds pushed a commit to branch 389-ds-base-1.3.10
in repository 389-ds-base.

The following commit(s) were added to refs/heads/389-ds-base-1.3.10 by this push:
     new 33b72ca  Issue 50745: ns-slapd hangs during CleanAllRUV tests
33b72ca is described below

commit 33b72ca8f64755bb7a13bf36190210ad1178b6da
Author: Mark Reynolds <mreynolds(a)redhat.com&gt;
AuthorDate: Tue May 19 11:25:13 2020 -0400

    Issue 50745: ns-slapd hangs during CleanAllRUV tests
    
    Bug Description:
    	The hang condition:
    		- is not systematic
    		- occurs in rare case, for example here during the deletion of a replica.
    		- a thread is waiting for a dblock that an other thread "forgot" to
    		  release.
    		- have always existed, at least since 1.4.0 but likely since 1.2.x
    
    	When deleting a replica, the replica is retrieved from
    	mapping tree structure (mtnode).
    	The replica is also retrieved through the mapping tree
    	when writing updates to the changelog.
    
    	When deleting the replica, mapping tree structure is cleared
    	after the changelog is deleted (that can take some cycles).
    	There is a window where an update can retrieve the replica,
    	from the not yet cleared MT, while the changelog being removed.
    
    	At the end, the update will update the changelog that is
    	currently removed and keeps an unfree lock in the DB.
    
    Fix description:
    	Ideally mapping tree should be protected by a lock but it
    	is not done systematically (e.g.  slapi_get_mapping_tree_node).
    	Using a lock looks an overkill and can probably introduce
    	deadlock and performance hit.
    	The idea of the fix is to reduce the window, moving the
    	mapping tree clear before the changelog removal.
    
    https://pagure.io/389-ds-base/issue/50745
    
    Reviewed by: Mark Reynolds, Ludwig Krispenz
---
 ldap/servers/plugins/replication/repl5_replica_config.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/ldap/servers/plugins/replication/repl5_replica_config.c
b/ldap/servers/plugins/replication/repl5_replica_config.c
index 80a0797..95b7fa5 100644
--- a/ldap/servers/plugins/replication/repl5_replica_config.c
+++ b/ldap/servers/plugins/replication/repl5_replica_config.c
@@ -735,18 +735,18 @@ replica_config_delete(Slapi_PBlock *pb __attribute__((unused)),
     PR_ASSERT(mtnode_ext);
 
     if (mtnode_ext->replica) {
+        Object *repl_obj = mtnode_ext->replica;
         /* remove object from the hash */
         r = (Replica *)object_get_data(mtnode_ext->replica);
+        mtnode_ext->replica = NULL;
         PR_ASSERT(r);
         /* The changelog for this replica is no longer valid, so we should remove it. */
         slapi_log_err(SLAPI_LOG_WARNING, repl_plugin_name, "replica_config_delete -
"
                                                            "The changelog for
replica %s is no longer valid since "
                                                            "the replica config is
being deleted.  Removing the changelog.\n",
                       slapi_sdn_get_dn(replica_get_root(r)));
-        cl5DeleteDBSync(mtnode_ext->replica);
+        cl5DeleteDBSync(repl_obj);
         replica_delete_by_name(replica_get_name(r));
-        object_release(mtnode_ext->replica);
-        mtnode_ext->replica = NULL;
     }
 
     PR_Unlock(s_configLock);

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