Re: deadlock in transaction.lock

Armin Waibel Thu, 04 Dec 2003 16:13:09 -0800

Hi,

I think first we need a test case to reproduce your deadlock.
Did you write such a test. If not, I will try to write such a test ASAP.

OJB has junit-extension classes to enable writing of multithreaded junit tests (e.g. see MetadataMultithreadedTest).

regards,
Armin

Jair da Silva Ferreira Júnior wrote:

Hi,

    The deadlock occurs when locking the objects. More specifically, in the
first write-lock of the object which happens to persists it.
    These are my locking properties in OJB.properties:
        LockManagerClass=org.apache.ojb.odmg.locking.LockManagerDefaultImpl
        LockMapClass=org.apache.ojb.odmg.locking.InMemoryLockMapImpl
        LockTimeout=60000
        ImplicitLocking=true
        LockAssociations=READ

Thanks,
    Jair Jr

----- Original Message -----
From: "Armin Waibel" <[EMAIL PROTECTED]>
To: "OJB Users List" <[EMAIL PROTECTED]>
Sent: Tuesday, December 02, 2003 8:41 PM
Subject: Re: deadlock in transaction.lock

Hi,

Jair da Silva Ferreira Júnior wrote:
Hi,
   I am using ojb1.0_rc4, ODMG api with OJB queries, mysql4 in Linux

Red Hat 7.3 (kernel 2.4.20-20.7).

I am experiencing the following problem: when multiple threads


(about 20) try to write lock an object, at some point, the
transaction.lock(object,Transaction.WRITE) method simply doesn't return and
my thread never dies. This is causing my application to deadlock. I am
locking different objects in each thread.

Did the deadlock occur while locking the objects
or when commit the transaction? Which lock map
implementation do you use?
regards,
Armin
I have tried the following <connection-pool> configurations in

repository_database.xml with no success:

<connection-pool maxActive="50" validationQuery=""

whenExhaustedAction="1" maxWait="4000"/>

<connection-pool maxActive="3" validationQuery=""

whenExhaustedAction="2" maxWait="4000"/>

Do you know why this is happening? The transaction.lock(..) method


should throw an exception if the object can't be locked, right? Any help
would be appreciated.

Thanks,
   Jair Jr


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Re: deadlock in transaction.lock

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