[jboss-jira] [JBoss JIRA] Commented: (JGRP-690) Thread interrupt status is not always cleared by default

Thread interrupt status is not always cleared by default -------------------------------------------------------- Key: JGRP-690 URL: http://jira.jboss.com/jira/browse/JGRP-690 Project: JGroups Issue Type: Bug Affects Versions: 2.6, 2.7 Reporter: Vladimir Blagojevic Assigned To: Vladimir Blagojevic Fix For: 2.7, 2.6.2 If Thread#interrupt() is invoked on a thread that is blocked in an invocation of the wait(), wait(long), or wait(long, int) methods of the Object class, or of the join(), join(long), join(long, int), sleep(long), or sleep(long, int), methods of this class, then its interrupt status will be cleared and it will receive an InterruptedException. (citing Thread#interrupt javadoc) Conventional wisdom was that interrupt signal was always cleared. However, in cases except the above interrupt signal is actually not cleared! JGroups code that is throwing InterruptedException should make sure that it also clears the interrupt status. Otherwise, if we wrongly assume that interrupt status is always cleared, we can have inconsistencies that can lead to hard-to-trace bugs (See below). We should verify that throughout our code that we always clear interrupt status. Gray said on javagroups-list: We have been seeing a large percentage of our production servers (on 2.6.1) spinning above 100% of CPU. After some investigation, we seem to have found an infinite loop in Scheduler.java. If sched_thread gets interrupted, its interrupt flag never gets reset so it spins forever suspending and resuming the current_thread and throwing and catching InterruptedException(s). According to jconsole, one of our boxes has done this 690 million times -- nice effort. When this is happening, the memory space is alternating between 200 and 300 mb which makes sense given the exception bandwidth. We are running our RPC dispatchers wth deadlock_detection and concurrent_processing set to true and use_concurrent_stack="true". Here are http://www.nabble.com/file/p15395455/stack_dumps.txt some stack snapshots of the spinning thread . As you can see they are all in Scheduler.run. Here is the section from http://www.nabble.com/file/p15395455/Scheduler.java.txt Scheduler.java with the offending part of the code including where sched_thread is being interrupted by a call to Scheduler.addPrio(). The pluses show where we think a missing Thread.interrupt() call should be. Here's the http://www.nabble.com/file/p15395455/Scheduler.java.patch.txt patch for Scheduler.java (from 2.6.1) which adds in the interrupt call. This is all with Jgroups 2.6.1. Anyone else see this behavior? We're going to roll this patch out to see if it stops the spinning. gray