Deven, Thank you!
On 2012-04-26 05:21, Deven You wrote: > Hi Dmitry, > > Thanks for your help. I have created a CR with internal id 2236492 which > hasn't be published yet. So please set this internal CR id as duplicate > to 716419 as well. > > This is the original mail for this problem: > > > > ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- > > Hi core-libs-devs, > > I am not sure if sun.management.Agent belongs to jmx-dev mailing list, > if so please anyone tell me. > > This issue is that the sun.management.Agent.loadManagementProperties() > will invoke properties.putAll which will throw > ConcurrentModifcationException if there are other threads which modify > the properties concurrently. > > I have made a patch[1] which synchronize the sysProps so that putAll can > work on multi-thread scenario. The test case is also available in [1]. > > Thanks a lot! > > [1] http://cr.openjdk.java.net/~littlee/OJDK-256/webrev.00 > <http://cr.openjdk.java.net/%7Elittlee/OJDK-256/webrev.00> > > ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- > > > Thanks a lot! > > > > On 04/25/2012 08:32 PM, Dmitry Samersoff wrote: >> Deven, >> >> CR number is 7164191 . >> >> Could you re-send me your original e-mail with problem description and >> webrev link. >> >> I'll put it to CR comment field. >> >> >> -Dmitry >> >> >> >> On 2012-04-24 16:15, Dmitry Samersoff wrote: >>> Deven, >>> >>> After close look and off-line discussion with David Holmes, >>> the changes looks good for me. >>> >>> I'll take care of the rest. >>> >>> We have one more place in Agent.java executing exactly the same code >>> so I'll change both of them on your behalf. >>> >>> -Dmitry >>> >>> >>> On 2012-04-23 11:43, Deven You wrote: >>>> Thanks David, >>>> >>>> So is it ok for you to contribute this patch? >>>> >>>> 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 >>>>> ----- >>>>> >>>>> 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 >>>> >>> >> > > -- Dmitry Samersoff Java Hotspot development team, SPB04 * There will come soft rains ...
