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.03/

Incremental:
http://cr.openjdk.java.net/~mlarsson/8145083/webrev.02-03/

ConfigurationLocker renamed to ConfigurationLock to avoid confusion with 
the MutexLocker family of classes.
Semaphore and locking thread id moved into the ConfigurationLock; added 
a function to check if current thread has the lock when asserts are enabled.

Regards,
Marcus


On 2015-12-14 16:30, Marcus Larsson wrote:
> Hi again,
>
> Made some changes to the patch after feedback from Markus Grönlund. 
> The ConfigurationLocker and the semaphore have been moved out of the 
> LogConfiguration.hpp and into the .cpp instead. The lock is only used 
> internally by the LogConfiguration so this makes sense. It simplifies 
> the LogConfiguration interface and hides the details of the locking 
> under the hood.
>
> New webrev:
> http://cr.openjdk.java.net/~mlarsson/8145083/webrev.02/
>
> Incremental:
> http://cr.openjdk.java.net/~mlarsson/8145083/webrev.01-02/
>
> Thanks,
> Marcus
>
> On 2015-12-14 15:53, Marcus Larsson wrote:
>> 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
>>
>