Messages in this thread | | | Date | Thu, 11 Oct 2018 11:35:00 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH RFC] panic: Avoid extra noisy messages due to stopped cpus |
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On Thu, Oct 11, 2018 at 03:17:48PM +0800, Feng Tang wrote: > Sometimes when debugging kernel panic, we saw many extra noisy error > messages after the expected end: > > [ 35.743249] ---[ end Kernel panic - not syncing: Fatal exception > [ 35.749975] ------------[ cut here ]------------ > > These messages may overflow the sceen (framebuffer) and make debugging > much difficulter.
*blink* you actually using the framebuffer for debugging ?! Why the heck are you doing that?
> diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c > index c93fcfd..b703862 100644 > --- a/arch/x86/kernel/process.c > +++ b/arch/x86/kernel/process.c > @@ -520,6 +520,7 @@ void stop_this_cpu(void *dummy) > * Remove this CPU: > */ > set_cpu_online(smp_processor_id(), false); > + set_cpu_active(smp_processor_id(), false); > disable_local_APIC(); > mcheck_cpu_clear(this_cpu_ptr(&cpu_info)); >
WTH is stop_this_cpu() and how do we even get here with active still set?
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index 7fc4a37..cf41b7b 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -9034,7 +9034,7 @@ static inline int find_new_ilb(void) > { > int ilb = cpumask_first(nohz.idle_cpus_mask); > > - if (ilb < nr_cpu_ids && idle_cpu(ilb)) > + if (ilb < nr_cpu_ids && idle_cpu(ilb) && cpu_online(ilb)) > return ilb; > > return nr_cpu_ids;
Similar, this is the result of taking the CPU away without going through the normal path. You're doing something dodgy.
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