Eric,

Yes, I realized that a while back and never got around to fixing it.

Please try the (mostly untested) attached patch against 2.5.67 but it 
should apply to older versions as well.

Let me know how it goes, especially on SMP.

PS: there is a dedicated mailing-list for perfmon.
    Visit http://www.hpl.hp.com/research/linux/perfmon for details.

--
-Stephane