[jira] [Commented] (DIRSERVER-2418) Potential Synchronization Issue At AbstractBTreePartition

["Emmanuel Lécharny (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/DIRSERVER-2418?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17945519#comment-17945519 ] 

Emmanuel Lécharny commented on DIRSERVER-2418:
----------------------------------------------

Hi,

this is a real issue. I think this change would fix it:


{code:java}
    public String getSuffixId( PartitionTxn partitionTxn ) throws LdapException
    {
        if ( suffixId == null )
        {
            ParentIdAndRdn key = new ParentIdAndRdn( Partition.ROOT_ID, suffixDn.getRdns() );

            try
            {
                rwLock.readLock().lock();
                
                if ( suffixId == null )
                {
                    suffixId = rdnIdx.forwardLookup( partitionTxn, key );
                }
            }
            finally
            {
                rwLock.readLock().unlock();
            }
        }

        return suffixId;

{code}

Note that the {{suffixId}} variable is declared {{volatile}} which guarantees hat there can't be a partial initialization.


> Potential Synchronization Issue At AbstractBTreePartition 
> ----------------------------------------------------------
>
>                 Key: DIRSERVER-2418
>                 URL: https://issues.apache.org/jira/browse/DIRSERVER-2418
>             Project: Directory ApacheDS
>          Issue Type: Bug
>            Reporter: Mikhail Titov
>            Priority: Major
>
> Let's take a look at the [getSuffixId|https://github.com/apache/directory-server/blob/38e7e2bdb685f71c8f7726197bfbd22cce33ba3a/xdbm-partition/src/main/java/org/apache/directory/server/core/partition/impl/btree/AbstractBTreePartition.java#L2995] method:
> Field *suffixId* has been compared without locking at [link|https://github.com/apache/directory-server/blob/38e7e2bdb685f71c8f7726197bfbd22cce33ba3a/xdbm-partition/src/main/java/org/apache/directory/server/core/partition/impl/btree/AbstractBTreePartition.java#L2997] and is assigned under lock at [link|https://github.com/apache/directory-server/blob/38e7e2bdb685f71c8f7726197bfbd22cce33ba3a/xdbm-partition/src/main/java/org/apache/directory/server/core/partition/impl/btree/AbstractBTreePartition.java#L3004]. 
> This potentially may lead to a synchronization error, when many processes simultaneously pass the check and then reach the lock one by one.
> The problem and possible resolve are described in more detail [here|https://stackoverflow.com/questions/13261300/is-it-okay-to-double-check-before-and-inside-a-lock-before-running-the-code-in#:~:text=The%20first%20method,a%20performance%20issue.]



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