Not sure what is causing it, but my Haswell system has started to freeze up when running “wspy –config topdown.config”. This started happening after I updated the system and started running benchmarks after a month on the road.

Some additional diagnosis and items I’ve tried:

1. Observed that the hangs also happened in a debugger running single-step so investigated how many single-steps before it hung. That may have been a false lead, as the single step in middle of fopen(3C) suddenly jumps ahead. However, along the way, tightened up my strtok() calls to be strtok_r() to make sure nothing strange was happening with recursive open_config_file()/parse_command_line calls. These were set up to be tail-recursive, so shouldn’t matter but cleaned up anyways.
2. Next observed that failure seemed to happen in setting up performance counters. Created small test program that made the same performance counters, and it didn’t hang.
3. Looked through logs in /var/log and didn’t see any smoking guns. The kernel completely locks up, even for other logged in processes – so even if the program is faulty, there is vulnerability to locking the kernel.
4. Further analysis started looking at grub to boot to an older kernel. In the process, uncovered that I was running under Xen hypervisor. Booting into bare metal fixed the problem. I’ve added a check to my 123.sh script that calls wspy. Not sure why this hung the system, but I don’t have virtual counters enabled, so this shouldn’t work. TODO item to look at more robust error detection in wspy to avoid stumbling into this again.

Conclusion: running under bare metal fixed the issue.