I'm trying to write a systemtap script that will identify contended mutex locks 
and print a user stack trace to identify them. Two unsuccessful attempts are 
attached, I'd appreciate any tips on how to make them work.

futexes.stp is a modified version of the futexes example provided with stap. I 
added a pthread_mutex_lock.return trace point and I attempt to print the user 
stack trace there. However the stack trace is just a hex address. Also for my 
contention_test.c (attached) test it claims that there are 9 locks contended 1 
times each rather than 1 lock contended 9 times.

mutexes.stp sets probes on pthread_muted_lock and .return. This almost works but 
the stack trace for contention_test.c doesn't show functions main and foo as I 
expect, I get:
  0x0000003073408ca0 : __pthread_mutex_lock+0x0/0x135 [/lib64/libpthread-2.5.so]
  0x000000000040065e : _end+0x15de06/0x1e97a8 
[/home/remote/aconway/install/lib/libqpidbroker.so.2.0.0]

If I run mutexes.stp on anything non-trivial it prints a bunch of very promising 
looking stack traces but then falls over with:

ERROR: Skipped too many probes, check MAXSKIPPED or try again with stap -t for 
more details.
WARNING: Skipped due to global 'thread_blocktime' lock timeout: 101

Any tips on how to make these work would be greatly appreciated!