On 23/04/2012 5:43 PM, Deven You wrote:
Thanks David,
So is it ok for you to contribute this patch?
You can count me as a Reviewer, but it still needs sign-off from Mandy
as a serviceability representative.
I don't have the spare cycles to act as sponsor for this if you need
someone to push it.
David
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On 04/23/2012 02:36 PM, David Holmes wrote:
Except of course that Properties is a Hashtable and synchronizes on
'this' for all public methods. So locking the properties object in the
client code will guarantee exclusive access to it.
Sorry about that.
David
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On 23/04/2012 4:30 PM, David Holmes wrote:
Deven,
On 23/04/2012 3:54 PM, Deven You wrote:
On 04/18/2012 02:20 PM, Deven You wrote:
On 04/18/2012 01:34 PM, Mandy Chung wrote:
I think this could still run into CME. System Properties is not a
synchronized map and the setter methods (System.setProperty or
Properties.put method) doesn't synchronize on the Properties object.
The setter methods I'm referring to are System.setProperty and
System.getProperties().put().
I have gone through the Agent.java, I think other set/put methods
related to properties are protected properly.
public static void agentmain using parseString(args) which return a
properties which is a local var and is not possible to cause
concurrent problem when call config_props.putAll(arg_props).
private static synchronized void startLocalManagementAgent() is
synchronized already.
private static synchronized void startRemoteManagementAgent(String
args) is synchronized also.
Could you point where the CME may ocurr?
Is there any suggestion from the mailing list?
The problem is that System.getProperties() returns a globally accessible
set of properties. So even if you prevent the Agent code from modifying
those properties concurrently with other use in the Agent, you have no
such guard for any other piece of code in the system which might also
modify the properties. So the race condition you were trying to fix
still exists. I don't see any way to fix this. No matter what you do
another thread can modify the system properties while you are iterating
them. Instead you need to anticipate the CME and try to recover from it
(also non-trivial).
Cheers,
David Holmes
