<Sound Dev> RFR: 8266421: Deadlock in Sound System [v2]

[Sergey Bylokhov]

> 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?

Sergey Bylokhov has updated the pull request incrementally with one additional commit since the last revision:

  Update SetPositionHang.java

-------------

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/4141/files
  - new: https://git.openjdk.java.net/jdk/pull/4141/files/aedecbf4..2025e14a

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=4141&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=4141&range=00-01

  Stats: 3 lines in 1 file changed: 0 ins; 0 del; 3 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4141.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4141/head:pull/4141

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