Add in Helgrind checks

[jwbensley]

Can we add in some Helgrind checks due to the use of multiple-threads?

bensley@htpc-ubuntu:~/c/EtherateMT$ sudo valgrind --tool=helgrind ./build/etherate_mt -I 2
==26222== Helgrind, a thread error detector
==26222== Copyright (C) 2007-2013, and GNU GPL'd, by OpenWorks LLP et al.
==26222== Using Valgrind-3.10.1 and LibVEX; rerun with -h for copyright info
==26222== Command: ./build/etherate_mt -I 2
==26222== 
Using inteface eth1 (2).
Setting interface promiscuous mode
Frame size set to 1514 bytes.
Using raw packet socket with send()/read().
Running in Tx mode.
==26222== 
==26222== Process terminating with default action of signal 11 (SIGSEGV)
==26222==  Access not within mapped region at address 0x90
==26222==    at 0x4051B6: print_stats (print_stats.c:60)
==26222==    by 0x4C30FA6: ??? (in /usr/lib/valgrind/vgpreload_helgrind-amd64-linux.so)
==26222==    by 0x4E45183: start_thread (pthread_create.c:312)
==26222==    by 0x515903C: clone (clone.S:111)
==26222==  If you believe this happened as a result of a stack
==26222==  overflow in your program's main thread (unlikely but
==26222==  possible), you can try to increase the size of the
==26222==  main thread stack using the --main-stacksize= flag.
==26222==  The main thread stack size used in this run was 8388608.
==26222== 
==26222== For counts of detected and suppressed errors, rerun with: -v
==26222== Use --history-level=approx or =none to gain increased speed, at
==26222== the cost of reduced accuracy of conflicting-access information
==26222== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)

[jwbensley]

https://valgrind.org/docs/manual/hg-manual.html

[jwbensley]

Also do we need to use __sync_add_and_fetch with the stats thread?