Re: [merge] WARN arch/powerpc/kernel/irq_64.c:278

[Sachin Sant <sachinp@linux.ibm.com>]

> On 03-Feb-2023, at 3:55 PM, Nicholas Piggin <npiggin@gmail.com> wrote:
> 
> On Fri Feb 3, 2023 at 4:26 PM AEST, Sachin Sant wrote:
>> I am observing an intermittent crash while running powerpc/security
>> selftests on a Power10 LPAR booted with powerpc/merge branch code.
>> 
>> ------------[ cut here ]------------
>> WARNING: CPU: 1 PID: 5644 at arch/powerpc/kernel/irq_64.c:278 arch_local_irq_restore+0x254/0x260
> 
> Okay, I guess the static branch test changes from true to false both
> times it is tested and so it doesn't recover properly. It's a real bug.
> I don't know why I didn't change the static branch under stop machine,
> maybe it gets into some recursive issue, that would be ideal if we could
> though. But this might be a safer minimal fix?
> 
> Thanks,
> Nick
> —
> 

Thanks Nick. Since this failure was intermittent I ran the test 10 times
with and without this patch.

Without the patch failure rate was 3 out of 10
With the patch no failures were seen (0/10).

I also ran the remaining selftests and observed no additional failures.

Based on these tests this fixes the problem for me.

- Sachin