RFR: 8077846: improve locking strategy for readConfiguration(), reset(), and initializeGlobalHandlers() (original) (raw)

Peter Levart peter.levart at gmail.com
Mon May 4 13:26:02 UTC 2015

Hi Daniel, Mandy,

What about the following:

http://cr.openjdk.java.net/~plevart/misc/LogManager.synchronization/webrev.03/

You see, no boolean flags needed. The globalHandlersState is always changed atomically within a locked region, so a graph of transitions can be drawn:

http://cr.openjdk.java.net/~plevart/misc/LogManager.synchronization/LogManager.globalHandlersState.png

STATE_INITIALIZING and STATE_READING_CONFIG are intra-locked-region states used to prevent infinite recursion in initializeGlobalHandlers() and communicating state from within locked-region of readConfiguration() to nested reset(), respectively, but never from one locked region to another.

Regards, Peter

On 05/01/2015 02:03 AM, Peter Levart wrote:

On 04/30/2015 04:42 PM, Daniel Fuchs wrote: On 28/04/15 17:46, Peter Levart wrote:

On 04/28/2015 04:57 PM, Daniel Fuchs wrote: Here's my attempt at simplifying this:

http://cr.openjdk.java.net/~plevart/misc/LogManager.synchronization/webrev.01/

LogManager can be subclassed, and subclasses may override reset() for different purposes. So I'm afraid the Cleaner thread still needs to call te public reset() method. The same unfortunately applies to readConfiguration(). best regards, -- daniel Um, yes of course. This can be fixed: http://cr.openjdk.java.net/~plevart/misc/LogManager.synchronization/webrev.02/ Hi Peter, Sorry for the late reply. My gut feeling is that I dislike multi-state ints. But I guess that's a matter of taste - so I could probably overcome it ;-) Isn't that a simplification (of reasoning)? In particular if individual boolean flags are read and/or written without holding any lock. What makes me less happy is that I had managed to remove the explicit synchronized() { } block in the Cleaner thread - and I now see it's back. Could we maybe keep the imminentDeath boolean and remove the explicit locking in the Cleaner thread? I mean... imminentDeath should be checked from within the lock - before doing anything. But it does not need to be set from within a locked section. best regards, -- daniel Hi Daniel, Mandy, Explicit locking in Cleaner is something that is performed in reset() anyway, so getting rid of it is not actually getting rid of it, as Cleaner is calling reset() anyway. The lock is reentrant. But If you want get rid of it so that reset() is not called under lock held because reset() might be overridden, then imminentDeath must return. @Mandy: In webrev.01 we had a private reset(int newState), called from reset(), Cleaner and readConfiguration(), but Daniel then spotted that reset() is an overridable method, so it has to be called from Cleaner and readConfiguration() too, unfortunately. The STATEXXX names are best depicted if looking at code in initializeGlobalHandlers() method. Let me prepare a changed webrew... Regards, Peter

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