[DERBY-6679] Possible Atomicity Violation in BaseMonitor.shutdown()

• Type: Bug
• Status: Open
• Priority: Minor
• Resolution: Unresolved
• Affects Version/s: 10.10.2.0
• Component/s: Services
• Environment: all
• Urgency: Normal
• Assignee: Unassigned
• Reporter: Diogo Sousa
• Created: 29/Jul/14 07:53
• Updated: 29/Jul/14 16:04

Description

I'm developing a tool for atomicity violation detection and I think it have found an atomicity violations in derby.

In org.apache.derby.impl.services.monitor.BaseMonitor there might be an atomicity violation in method shutdown(), lines 181-206:

		for ( ; ; ) {
			synchronized (this) {
 181:    		position = services.size()  - 1;
			if (position == 0)
				break;
                               ...
	        	}
                       ...
	        }
	       ...
206:	      ((TopService) services.get(0)).shutdown();

Between the execution of lines 181 and 206 a concurrent thread may remove the only remaining service, causing the access to "services" in line 206 to fail.