Jim Crossley wrote:
Well, it would seem to me that a ThreadLocal instance could help solve this problem. If one thread tries to acquire a lock it already owns, it ought to get it, right
No, the lock belongs to the tx! This is exactly the semantic you request with "RequiresNew". The ThreadLocal exists, but the suspend on tx1 takes the association out of the ThreadLocal and associates a new tx2 with the thread.
If we were to apply the same semantics you describe to a simple Java class, then calling setX would always block...class C { synchronized void setX() { setY(); } synchronized void setY() { ; } } If this is really the way JBoss works, and nobody knows a good reason why it should, can someone point me to the package/class responsible for this behavior and I'll take a whack at fixing it?
I think there might be something to fix with your tx markup. Change "RequiresNew" to "Requires", so the same tx will get used throughout your call.
Thanks, Jim On Thu, 2002-10-24 at 15:40, Michael Bartmann wrote:Explanation attempt inline. Regards, Michael Bartmann Jim Crossley wrote:I have an MDB with the following pseudocode in its onMessage method: public void onMessage(Message msg) { // Entity bean = home.create(...) // bean.setX(...)this starts a tx1 and locks the instance bean.// bean.setY(...)this suspends the tx1 on bean temporarily, and starts a tx2, which tries to obtain the lock on the bean, which it will never get, because tx1 is not commited or rollbacked yet. We had this problem under 2.4.4 w/o deadlock detection. Problem: even the tx timeout didn't work in this case; the server locked forever... :-(}
Each of the three methods, create, setX, and setY have a trans-attribute
of "RequiresNew". With only one client posting a message, a "deadlock
detected" exception is thrown when setX is invoked. How can deadlock
occur when only one thread is active
Thanks,
Jim
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