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SubjectRe: [PATCHv2] perf/x86/intel: Account interrupts for PEBS errors
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

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