<Sound Dev> Integrated: 8266421: Deadlock in Sound System

[Sergey Bylokhov]

On Fri, 21 May 2021 08:15:25 GMT, Sergey Bylokhov <serb at openjdk.org> wrote:

> In the fix for JDK-8207150 I have updated the synchronization of some code paths under one "lock", before that code was synchronized only on some threads and missing on others. Old review:
> http://mail.openjdk.java.net/pipermail/sound-dev/2018-August/000650.html
> 
> That fix introduced this order of locks: "lock"->"synchronized(this)", I have checked other places and did not found where we use the opposite order. Unfortunately, one such place exists in the private subclass DirectClip.
> 
> I have checked both usages of synchronized which caused deadlock:
>  - In the DirectClip class the method setMicrosecondPosition is marked as "synchronized" but it is unclear why. This method is implemented as a call to another public method setFramePosition which is not "synchronized" and use some internal synchronization. So I have removed this keyword.
>  - In a few places we have the code like this:
> 
>         boolean sendEvents = false;
>         synchronized (this) {
>             if (this.started != started) {
>                 this.started = started;
>                 sendEvents = true;
>             }
> 	}
>         if (sendEvents) {.....
> 
> I doubt that this type of synchronization may help something - the fields are volatile and we use sendEvents flag after synchronisation block, so I removed it as well. Any thoughts?

This pull request has now been integrated.

Changeset: f6f82c31
Author:    Sergey Bylokhov <serb at openjdk.org>
URL:       https://git.openjdk.java.net/jdk/commit/f6f82c31689e68f4263bbbe2314033d69f9049f5
Stats:     128 lines in 4 files changed: 106 ins; 11 del; 11 mod

8266421: Deadlock in Sound System

Reviewed-by: prr, azvegint

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PR: https://git.openjdk.java.net/jdk/pull/4141