On Thu, 15 Dec 2016, Jiri Olsa wrote: > It's possible to setup PEBS events and get only errors and not > a single data, like on SNB-X (model 45) and IVB-EP (model 62) > via 2 perf commands running simultaneously: > > taskset -c 1 ./perf record -c 4 -e branches:pp -j any -C 10 > > This leads to soft lock up, because the error path of the > intel_pmu_drain_pebs_nhm does not account event->hw.interrupt > for error PEBS interrupts so the event is not eventually > stopped when it gets over the max_samples_per_tick limit. > > NMI watchdog: BUG: soft lockup - CPU#22 stuck for 22s! [perf_fuzzer:5816] > ... > task: ffff880273148000 task.stack: ffffc90002d58000 > RIP: 0010:[<ffffffff81159232>] [<ffffffff81159232>] > smp_call_function_single+0xe2/0x140 > RSP: 0018:ffffc90002d5bd60 EFLAGS: 00000202 > ... > Call Trace: > ? trace_hardirqs_on_caller+0xf5/0x1b0 > ? perf_cgroup_attach+0x70/0x70 > perf_install_in_context+0x199/0x1b0 > ? ctx_resched+0x90/0x90 > SYSC_perf_event_open+0x641/0xf90 > SyS_perf_event_open+0x9/0x10 > do_syscall_64+0x6c/0x1f0 > entry_SYSCALL64_slow_path+0x25/0x25
I'll have to try this, with all the recent fixes I am down to NMI lockups like this being the major cause of fuzzer issues on my intel machines. My AMD and ARM machines are now fuzzing for weeks w/o problems. I also finally got a power8 machine and it crashes really quickly when fuzzing, but I haven't had a chance to track dthings own yet because it sounds like a jet plane taking off and I can't really leave it fuzzing like that when students are sitting nearby. Maybe over break. Vince
