RFR: 8145083: Use semaphore instead of mutex for synchronization of Unified Logging configuration

[Marcus Larsson]

Hi,

New webrev:
http://cr.openjdk.java.net/~mlarsson/8145083/webrev.01/

Incremental:
http://cr.openjdk.java.net/~mlarsson/8145083/webrev.00-01/

Changes:
* Introduced the ConfigurationLocker class for automatic wait/signal in 
constructor/destructor just like a MutexLocker.
* Added an assert to verify that the "lock" is held by the current 
thread when calling configure_output.
* Made the config-string functions in LogOutput protected and 
LogConfiguration a friend of LogOutput to prevent incorrect usage of 
these functions. These functions should typically only be used inside 
configure_output, which now ensures that the lock is held.

Thanks,
Marcus


On 2015-12-14 11:13, Marcus Larsson wrote:
> Hi,
>
> Please review the following patch to use a semaphore instead of a 
> mutex for the synchronization of log configuration. Using a mutex 
> requires some parts of the VM to be initialized, whereas the 
> semaphores can be used right from the start. This simplifies the code 
> and allows very early log configuration without special cases for 
> early configuration vs reconfiguration after VM init.
>
> Webrev:
> http://cr.openjdk.java.net/~mlarsson/8145083/webrev.00/
>
> Issue:
> https://bugs.openjdk.java.net/browse/JDK-8145083
>
> Thanks,
> Marcus