Re: [wtp-dev] Request PMC approval for 130994 - please review deadlock i

[Chuck Bridgham <cbridgha@xxxxxxxxxx>]

Hi David,

Well this is a problem with all of our
code in WTP, we don't have a general locking policy, and I am trying to
solve this particular use case. 
I want more eyes on it from the BEA
side, since they have the reproducible scenario.

I kept the object locks just for that
case where all clients are not using scheduling rules.  I believe
this patch will solve the problem BEA was encountering,
but I don't claim it can fix all locking
issues, and until WTP/eclipse has a general policy, this is a very hard
problem.

- Chuck

Rational J2EE Tooling Team Lead
IBM Software Lab - Research Triangle Park, NC
Email:  cbridgha@xxxxxxxxxx
Phone: 919-254-1848 (T/L: 444)

David M Williams/Raleigh/IBM@IBMUS
Sent by: wtp-dev-bounces@xxxxxxxxxxx

04/02/2006 11:01 PM

Please respond to
"General discussion of project-wide or architectural issues."

To	"General discussion of project-wide or architectural issues." <wtp-dev@xxxxxxxxxxx>
cc
Subject	Re: [wtp-dev] Request PMC approval for 130994 - please review deadlock        issues

I would appreciate further review of this fix. 

As you state, its follows a pattern of 

        acquire SchedulingRule
            synchronized (some object) 
                {meaty stuff}
        release ScheduleingRule

I think this is still deadlock prone, unless *all* clients use exact same
pattern. 

If, for example, somewhere else, only synchronized is used, AND ends up
calling back to this code, then I think deadlock will occur. 
Is it known (or, at least documented) that this is the pattern all clients
should use? 
My guess is not, and that's why you are using synchronized block to begin
with. 
Or, perhaps, synchronized part is not needed at all? And could do all with
scheduleing rules? 

I must confess, this was from my quick reivew of the patch ... so I may
be mis-reading it, or 
these issues may be well (better!) understood, 
but just thought I'd request the education for myself. 

Thanks,

Chuck Bridgham/Raleigh/IBM@IBMUS
Sent by: wtp-dev-bounces@xxxxxxxxxxx

03/30/2006 12:00 PM

Please respond to
"General discussion of project-wide or architectural issues." <wtp-dev@xxxxxxxxxxx>

To	"General discussion of project-wide or architectural issues." <wtp-dev@xxxxxxxxxxx>
cc
Subject	[wtp-dev] Request PMC approval for 130994

Have fix that first acquires lock based on scheduling rules, then uses
the object monitor locks. finally it releases the lock through the  JobManager.
This will avoid deadlocks with other processes that also use scheduling
rules. 

Tested locally 

Thanks - Chuck 

Rational J2EE Tooling Team Lead
IBM Software Lab - Research Triangle Park, NC
Email:  cbridgha@xxxxxxxxxx
Phone: 919-254-1848 (T/L: 444)_______________________________________________
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