RFR(s): 8151264: Add a notification mechanism for UL configuration changes

[David Holmes]

Hi Robbin,

On 9/03/2016 7:02 PM, Robbin Ehn wrote:
>
> Hi, please review this minor change.

A notification mechanism is not so minor - what are the programming 
rules for the callbacks? which threads might execute them? Are there any 
obvious deadlock/livelock potentials? Do we need to unregister a callback?

At a minimum there should be some comments regarding the nature of the 
callback and what it can and can't do.

> Bug: https://bugs.openjdk.java.net/browse/JDK-8151264/
> Webrev: http://cr.openjdk.java.net/~rehn/8151264/webrev/

Some minor nits:

src/share/vm/logging/log.cpp

Copyright needs 2016 added.

---

src/share/vm/logging/logConfiguration.cpp

+   assert(cb != NULL, "Should not initialize register NULL as listener.");

"initialize register" doesn't make grammatical sense - delete "initialize"

+   for (size_t i=0;i<_n_listener_callbacks;i++) {

Style nits: spaces around operators and after ;

---

src/share/vm/logging/logConfiguration.hpp

+   // After any configuration change this method should be called by in 
scope of LogConfigurationLock

Delete 'by' - or may I suggest:

// This should be called after any configuration change while still 
holding ConfigurationLock

Thanks,
David
-----

> Tested with a new internal vm test (included).
>
> Thanks!
>
> /Robbin