Re: WARNING: at arch/x86/kernel/cpu/perf_event.c:989

From: Stephane Eranian
Date: Mon Feb 06 2012 - 16:25:49 EST

On Mon, Feb 6, 2012 at 9:58 PM, Peter Zijlstra <a.p.zijlstra@xxxxxxxxx> wrote:
> On Mon, 2012-02-06 at 21:44 +0100, Stephane Eranian wrote:
>> Which is pointing to the Intel specific:
>> intel_pmu_handle_irq()
>> again:
>> Â Â Â Â intel_pmu_ack_status(status);
>> Â Â Â Â if (++loops > 100) {
>> Â Â Â Â Â Â Â Â WARN_ONCE(1, "perfevents: irq loop stuck!\n");
>> Â Â Â Â Â Â Â Â perf_event_print_debug();
>> Â Â Â Â Â Â Â Â intel_pmu_reset();
>> Â Â Â Â Â Â Â Â goto done;
>> Â Â Â Â }
>> We are in a constant interrupt loop for a reason I don't yet understand.
>> Sure we have two counters going, bu given the callstack, one is being
>> stopped.
>> I know we talked about that a couple of weeks back, but after all, it may
>> be that it is not possible to run the frequency adjustment code without
>> stopping the entire PMU because of risk of interrupts. But it is not clear
>> to me what's causing this at this point.
> There's Errata's on this, see AAK157 (SNB) BD106 (WSM) AAK157 (NHM).
Arg, I had forgotten about those.....
I'll check on this further with Intel.

> Ingo and I talked about a 'fix' for that based on the text in the SNB
> errata which explains why the reset works. Ingo I was under the
> impression you were going to implement that?
>> I suggest we still apply my patch to fix the x86_pmu_start() first, then
>> I will submit a second patch to fix that one. Agreed?
> Yes.
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at