I have a program that uses STM heavily and also performs lots of foreign calls. I've noticed that sometimes the program uses 100% CPU indefinitely and uses lots of memory - I see it go up to about 5GB before I kill it. I've grabbed some preliminary samples of stack traces and see lots stm related stuff (e.g. lots of stg_atomically_frame_info and stmCommitTransaction entries).  I can pretty reliably get the behavior to happen now by closing a socket that my Haskell program is trying to recv from. When this causes an exception to be raised (something like "recv: resource vanished (Connection reset by peer)") , then this behavior gets triggered.  I haven't pinned down the bug yet, but I'm suspecting it is STM related - somehow the exception causes some STM transaction to go wrong. 

Are there any known bugs that sound similar to this? 

BTW, this is with GHC 7.6.3 from a recent HP release on OS X.

-Andi