[ZOOKEEPER-1191] Synchronization issue - wait not in guarded block

• Type: Sub-task
• Status: Resolved
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 3.4.0
• Fix Version/s: 3.5.0
• Component/s: server
• Assignee: Alexander Shraer Assign to me
• Reporter: Alexander Shraer
• Created: 17/Sep/11 19:53
• Updated: 14/Apr/14 02:10
• Resolved: 14/Apr/14 02:10

Description

In Leader.java, getEpochToPropose() and waitForEpochAck() have the following code:

if (readyToStart && verifier.containsQuorum(electingFollowers)) {
electionFinished = true;
electingFollowers.notifyAll();
} else {
electingFollowers.wait(self.getInitLimit()*self.getTickTime());
if (waitingForNewEpoch)

{ throw new InterruptedException("Out of time to propose an epoch"); }

}

In Java, the wait statement can wake up without being notified, interrupted, or timing out, a so-called spurious wakeup. So it should be guarded by a while loop with the condition we're waiting for.