[jcifs] Hung threads accessing domain controller

[Michael B Allen]

On Thu, 13 Jan 2005 10:37:29 -0600
"Christensen, Scott M" <SCHRIST1 at amfam.com> wrote:

> > What evidence do you have to suggest that these threads are never
> released?
> 
> Websphere has a thread monitor that analyzes the current threads and
> responds if threads appear to be in a hung state.  We are seeing the
> number of hung threads increase over a period of days to the point where
> every thread is in a hung state.  Here is the message that is reported
> 
> [1/13/05 8:46:05:009 CST]  10f405e ThreadMonitor W WSVR0605W: Thread
> "Servlet.Engine.Transports : 27795" (83978c) has been active for 760,739
> milliseconds and may be hung.  There are 32 threads in total in the
> server that may be hung.
> 
> This number increases sequentially and never goes down.  Every one of
> the threads is hanging on an Object.wait() call (SmbTransport.java:877).

This is indeed hanging threads. When multiple threads try to call into
the jCIFS library only one is allowed to perform the negotiation with
the DC. The others are asked to wait at SmbTransport.java:877 but never
notified when the negotiation is complete (so they can simply return).

I believe the fix is to add a notify:

    947         state = ST_NEGOTIATED;
    948         notify();
    949     }

I'll have to look at this closer and test it out a little.

> Line 877 in SmbTransport.java is a call to a never ending wait().  I am
> assuming that there is another thread that will notify the thread that
> this wait() corresponds to, but I am unable to find where that call may
> happen.  And if it happens to be associated with the
> jcifs.smb.client.responseTimeout, it appears that this timeout is not
> happening.

You are correct and there is no notify(). Nice catch Scott.

Mike

-- 
Greedo shoots first? Not in my Star Wars.