[mythtv] Valgrind/helgrind vs NPTL trace

[faginbagin]

I'm in the process of tracking down a deadlock in mythvideo. So far, I 
think I've confirmed it is the result of two threads trying to take 
mutex locks already taken by the other thread. Now I'm looking at tools 
to help me gather more details. So far, I've come across valgrind's 
helgrind and NPTL trace. I'm still reading up on valgrind and have yet 
to look at NPTL trace. I'm concerned that valgrind might slow things 
down to the point where it really won't help, given the nature of 
mythtv, and maybe NPTL trace might have the same issue. So I thought I'd 
ask if anyone has used either of these tools successfully to debug 
thread deadlocks, or if there's another tool or technique that is more 
useful. Any recommendations for debugging thread deadlocks would be most 
welcome.

TIA,
Helen