Mailing-List: contact dev-help@cocoon.apache.org; run by ezmlm
Precedence: bulk
Reply-To: dev@cocoon.apache.org
Message-ID: <817350192.1212771825120.JavaMail.jira@brutus>
Date: Fri, 6 Jun 2008 10:03:45 -0700 (PDT)
From: "Sylvain Wallez (JIRA)" <jira@apache.org>
To: dev@cocoon.apache.org
Subject: [jira] Created: (COCOON-2208) Race condition in
 AbstractCachingProcessingPipeline causes threads to hang.
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 7bit

Race condition in AbstractCachingProcessingPipeline causes threads to hang.
---------------------------------------------------------------------------

                 Key: COCOON-2208
                 URL: https://issues.apache.org/jira/browse/COCOON-2208
             Project: Cocoon
          Issue Type: Bug
          Components: * Cocoon Core
    Affects Versions: 2.1.11
            Reporter: Sylvain Wallez
            Priority: Blocker


There's a race condition in AbstractCachingProcessingPipeline.waitForLock() : if "lock" is not null, there is a possibility that the thread that created the lock releases it before the current thread starts waiting on it (see below). When this happens, the thread waits forever since no thread will ever call notify() on the lock.

The very bad effect is that this progressively blocks the entire thread pool of the servlet engine, which ends up rejecting new incoming connections.

And BTW, calling containsKey() just before get() unneedingly doubles the number of lookups.

{noformat}
    protected boolean waitForLock(Object key) {
    	if(transientStore != null) {
    		Object lock = null;
    		synchronized(transientStore) {
    			String lockKey = PIPELOCK_PREFIX+key;
    			if(transientStore.containsKey(lockKey)) {
                	// cache content is currently being generated, wait for other thread
                	lock = transientStore.get(lockKey);
    			}
    		}
// START OF RACE CONDITION ZONE
        	if(lock != null) {
        		try {
        			// become owner of monitor
        			synchronized(lock) {
// END OF RACE CONDITION ZONE
        				lock.wait();
        			}
        		} catch (InterruptedException e) {
        			if(getLogger().isDebugEnabled()) {
        				getLogger().debug("Got interrupted waiting for other pipeline to finish processing, retrying...",e);
        			}
        			return false;
				}
        		if(getLogger().isDebugEnabled()) {
    				getLogger().debug("Other pipeline finished processing, retrying to get cached response.");
    			}
        		return false;
        	}
    	}
    	return true;
    }
{noformat}

-- 
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.