[jira] [Commented] (SOLR-11782) LatchWatcher.await doesn’t protect against spurious wakeup

["David Smiley (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/SOLR-11782?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16298660#comment-16298660 ] 

David Smiley commented on SOLR-11782:
-------------------------------------

Please use System.nanoTime() for measuring elapsed time, which is not affected by possible clock changes.  Otherwise, +1.

> LatchWatcher.await doesn’t protect against spurious wakeup
> ----------------------------------------------------------
>
>                 Key: SOLR-11782
>                 URL: https://issues.apache.org/jira/browse/SOLR-11782
>             Project: Solr
>          Issue Type: Bug
>      Security Level: Public(Default Security Level. Issues are Public) 
>            Reporter: Tomás Fernández Löbbe
>            Priority: Minor
>         Attachments: SOLR-11782.patch
>
>
> I noticed that {{LatchWatcher.await}} does:
> {code}
> public void await(long timeout) throws InterruptedException {
>       synchronized (lock) {
>         if (this.event != null) return;
>         lock.wait(timeout);
>       }
>     }
> {code}
> while the recommendation of lock.wait is to check the wait condition even after the method returns in case of spurious wakeup. {{lock}} is a private local field to which {{notifyAll}} is called only after a zk event is being handled. I think we should check the {{await}} method to something like:
> {code}
> public void await(long timeout) throws InterruptedException {
>       assert timeout > 0;
>       long timeoutTime = System.currentTimeMillis() + timeout;
>       synchronized (lock) {
>         while (this.event == null) {
>           long nextTimeout = timeoutTime - System.currentTimeMillis();
>           if (nextTimeout <= 0) {
>             return;
>           }
>           lock.wait(nextTimeout);
>         }
>       }
>     }
> {code}



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