[Click] SMP SpinLock and Deadlocks

[Paine, Thomas Asa]

	I have a click package, which contains my custom elements.
Those elements basically maintain maps of IP and data.  To protect the
maps during read/write handler operations, I have wrapped the critical
sections using the SpinLock found in the sync.hh.

My typical usage...

   ...
   _lock.acquire();
   bleMap->clear();
   _lock.release();
   ...


   ...
   _lock.acquire();
   bleMap->insert(n, type);
   _lock.release();
   ...



However, I'm experiencing periodic deadlocks and am seeing these types
of messages very frequently...

	"chatter: releasing someone else's lock" ...which is coming from
the SpinLock

I'm seeing these messages even when handlers are not being called and I
nice it a bit...  "echo -19 > /click/priority", so I'm not sure of the
scope of the problem.  Clearly calling _depth-- on the wrong lock would
lead to accounting problems with the semaphore and deadlock.
	The configuration is currently running on an appliance using the
latest CVS code and the 2.6.16.3 kernel.  The appliance is using an
Intel(R) Pentium(R) 4 CPU 3.20GHz with hyperthreading, and the kernel is
running with SMP support.  This configuration has been run on SMP
enabled machines before, but with 2 physical processors, and was still
using the 2.4 kernel, so I don't want to make too many comparisons
there.  I can say I have not experienced any behavior like this in the
past with the my elements or with click.  

The click and custom packages were last configured using the following,
and I've tried several variations of config options to see if I could at
least cause a change, but I haven't seemed to find what's broken.

"./configure --prefix=/backups/staging/click --disable-userlevel"

At this point, I'm not quite sure where the problem may lie.  Is this an
affinity problem with the click kernel module, SpinLock, hyperthreading,
kernel compilation option, or am I just not configuring/using something
correctly?  Has anyone else seen these messages unexpectedly? 



Thanks, 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
   Thomas Paine (paineta at uwec.edu) 
   University of Wisconsin - Eau Claire 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~