On Thu, Feb 20, 2014 at 11:25 PM, Kelly Boswell <[email protected]> wrote: > After the make test failed for this module, I decided to poke around to see > if there is an easy fix. I made a script that simply executes the test over > and over until it seg faults and exits after the core file is created. > > xxxxx@xxxx:~/src/gnuradio/build/gr-digital/python/digital$ ./runtests.sh > Using Volk machine: avx_64_mmx > Segmentation fault (core dumped) > > xxxxx@xxxx:~/src/gnuradio/build/gr-digital/python/digital$ gdb > /usr/bin/python2.7 core > (gdb) bt > (gdb) bt > #0 0x00007fe8f627fb17 in volk_32fc_32f_dot_prod_32fc_a_avx () > from /home/kelly/src/gnuradio/build/volk/lib/libvolk.so.0.0.0 > #1 0x00007fe8f52dd25f in > gr::filter::kernel::fir_filter_ccf::filter(std::complex<float> const*) () > from > /home/kelly/src/gnuradio/build/gr-filter/lib/libgnuradio-filter-3.8git.so.0.0.0 > #2 0x00007fe8f143c45b in > gr::digital::pfb_clock_sync_ccf_impl::general_work(int, std::vector<int, > std::allocator<int> >&, std::vector<void const*, std::allocator<void const*> >>&, std::vector<void*, std::allocator<void*> >&) () > from > /home/kelly/src/gnuradio/build/gr-digital/lib/libgnuradio-digital-3.8git.so.0.0.0 > #3 0x00007fe8f653809e in gr::block_executor::run_one_iteration() () > from > /home/kelly/src/gnuradio/build/gnuradio-runtime/lib/libgnuradio-runtime-3.8git.so.0.0.0 > #4 0x00007fe8f6573622 in > gr::tpb_thread_body::tpb_thread_body(boost::shared_ptr<gr::block>, int) () > from > /home/kelly/src/gnuradio/build/gnuradio-runtime/lib/libgnuradio-runtime-3.8git.so.0.0.0 > #5 0x00007fe8f6565ea1 in > boost::detail::function::void_function_obj_invoker0<gr::thread::thread_body_wrapper<gr::tpb_container>, > void>::invoke(boost::detail::function::function_buffer&) () > from > /home/kelly/src/gnuradio/build/gnuradio-runtime/lib/libgnuradio-runtime-3.8git.so.0.0.0 > ---Type <return> to continue, or q <return> to quit--- > #6 0x00007fe8f6526610 in boost::detail::thread_data<boost::function0<void> >>::run() () > from > /home/kelly/src/gnuradio/build/gnuradio-runtime/lib/libgnuradio-runtime-3.8git.so.0.0.0 > #7 0x00007fe8f9adc94a in ?? () > from /usr/lib/x86_64-linux-gnu/libboost_thread.so.1.53.0 > #8 0x00007fe8fc8a3f6e in start_thread (arg=0x7fe8e2ffd700) > at pthread_create.c:311 > #9 0x00007fe8fc5ce9cd in clone () > at ../sysdeps/unix/sysv/linux/x86_64/clone.S:113 > > Of course, I had to recompile it with debugging info to glean anything > useful from the stack trace. So, I did that and I traced the bug to this > line: > > c0Val = _mm256_mul_ps(a0Val, b0Val); > > I can't dump the values in a0Val or b0Val, though, because they're > intermediate values that are optimized away by the optimized kernel code. I > tried stepping through the assembler instructions but I'm not familiar with > the various sse and avx extensions. Heck, I'm not even familiar with the > x86_64 instruction set. So I have a huge learning curve ahead of me, there. > Is it possible to just dump the values in these __m256 data types to a file > so I can debug it that way? If that's not easy to do, then I'm willing to > learn what I have to about the instruction set so I can debug this thing. > But I would sure appreciate some help if anyone has some advice to offer. > > Software version: > I rebased to the latest version of the next branch last night before I went > to bed at around 1:30 am CDT. > > Operating System: > kelly@octs2:~/src/gnuradio/volk/kernels/volk$ uname -a > Linux octs2 3.11.0-17-generic #31-Ubuntu SMP Mon Feb 3 21:52:43 UTC 2014 > x86_64 x86_64 x86_64 GNU/Linux > It's Ubuntu 13.10 > > Hardware: ASUS X750J > Intel Quad Core i7 4700HQ 2.4GHz > > cpuinfo: > processor : 7 > vendor_id : GenuineIntel > cpu family : 6 > model : 60 > model name : Intel(R) Core(TM) i7-4700HQ CPU @ 2.40GHz > stepping : 3 > microcode : 0x8 > cpu MHz : 2401.000 > cache size : 6144 KB > physical id : 0 > siblings : 8 > core id : 3 > cpu cores : 4 > apicid : 7 > initial apicid : 7 > fpu : yes > fpu_exception : yes > cpuid level : 13 > wp : yes > flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov > pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx pdpe1gb > rdtscp lm constant_tsc arch_perfmon pebs bts rep_good nopl xtopology > nonstop_tsc aperfmperf eagerfpu pni pclmulqdq dtes64 monitor ds_cpl vmx est > tm2 ssse3 fma cx16 xtpr pdcm pcid sse4_1 sse4_2 x2apic movbe popcnt > tsc_deadline_timer aes xsave avx f16c rdrand lahf_lm abm ida arat epb > xsaveopt pln pts dtherm tpr_shadow vnmi flexpriority ept vpid fsgsbase > tsc_adjust bmi1 avx2 smep bmi2 erms invpcid > bogomips : 4789.27 > clflush size : 64 > cache_alignment : 64 > address sizes : 39 bits physical, 48 bits virtual > power management: >
Hi Kelly, First, this is great debugging, thanks for getting so much info and trying to go for a fix on your own. On to the good stuff. I was able to reproduce this on my i7-4700MQ. Here's some additional info for the logs: * constellation_receiver is a hier block with a fir_filter_ccf inside that is calling the volk avx dot product. * The avx dot product proto-kernel passes VOLK QA * The qa_fir_filter.py is testing a fir_filter_ccf that passes its QA. * Just for kicks, I forced VOLK to use the generic kernel and I still see the segfault. A couple of things I'd like to try (and please feel free to give these a try): * Go back to a commit just before fir_filter.cc started using volk_malloc and volk_free. (or for bonus points go back to some point in time when this test always passes and do a git bisect) * fiddle with parameters of the test, data length, number of taps in filter, etc. * Doubtful this would change, but test on different processors. It would be pretty wild if there was something off in the 4700 line, but the fact that the generic proto-kernel had the same result and nobody else has reported this yet is suspicious. My guess is GCC is actually emitting *very* similar code for the generic and avx dot product proto-kernels. Nathan _______________________________________________ Discuss-gnuradio mailing list [email protected] https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
