It looks like if the process was stopped to extract a back trace the ack signal is never delivered to frysk There was 1 failure: 1) testFerrorTracesPID_MissingSignal(frysk.bindir.TestFerror)junit.framework.AssertionFailedError: run until signal: assertSendAddCloneWaitForAcks(signals {SIGUSR1(10),SIGUSR2(12)}); outstanding: {SIGUSR2(12)} at frysk.testbed.SignalWaiter.assertRunUntilSignaled(TestRunner) at frysk.testbed.SlaveOffspring.spawn(TestRunner) at frysk.testbed.SlaveOffspring.assertSendAddCloneWaitForAcks(TestRunner) at frysk.bindir.TestFerror.testFerrorTracesPID_MissingSignal(TestRunner) at frysk.junit.Runner.runCases(TestRunner) at frysk.junit.Runner.runTestCases(TestRunner) at TestRunner.main(TestRunner) FAILURES!!! Tests run: 5, Failures: 1, Errors: 0