Python / OpenCV application lockup issue

I've managed to get a thread dump from gdb right at the point where 40+ threads are showing 100% 'system' CPU time.

Here's the backtrace which is the same for every one of those threads:

#0  0x00007fffebe9b407 in cv::ThresholdRunner::operator()(cv::Range const&) const () from /usr/local/lib/libopencv_imgproc.so.3.0#1  0x00007fffecfe44a0 in tbb::interface6::internal::start_for<tbb::blocked_range<int>, (anonymous namespace)::ProxyLoopBody, tbb::auto_partitioner const>::execute() () from /usr/local/lib/libopencv_core.so.3.0#2  0x00007fffe967496a in tbb::internal::custom_scheduler<tbb::internal::IntelSchedulerTraits>::local_wait_for_all(tbb::task&, tbb::task*) () from /lib64/libtbb.so.2#3  0x00007fffe96705a6 in tbb::internal::arena::process(tbb::internal::generic_scheduler&) () from /lib64/libtbb.so.2#4  0x00007fffe966fc6b in tbb::internal::market::process(rml::job&) () from /lib64/libtbb.so.2#5  0x00007fffe966d65f in tbb::internal::rml::private_worker::run() () from /lib64/libtbb.so.2#6  0x00007fffe966d859 in tbb::internal::rml::private_worker::thread_routine(void*) () from /lib64/libtbb.so.2#7  0x00007ffff76e9df5 in start_thread () from /lib64/libpthread.so.0#8  0x00007ffff6d0e1ad in clone () from /lib64/libc.so.6

My original question put Python and Linux front and center but the issue appears to lie with TBB and/or OpenCV. Since OpenCV with TBB is so widely used I presume it has to also involve the interplay with my specific environment somehow. Maybe because it's a 64 core machine?

I have recompiled OpenCV with TBB turned off and the problem has not reappeared so far. But my app now runs slower.

I have posted this as a bug to OpenCV and will update this answer with anything that comes from that.