Re: Fix 80d20d35af1e ("nohz: Fix local_timer_softirq_pending()") may have revealed another problem

[Heiner Kallweit]

On 24.08.2018 06:12, Frederic Weisbecker wrote:
> On Thu, Aug 16, 2018 at 08:13:03AM +0200, Heiner Kallweit wrote:
>> Recently I started to get warning "NOHZ: local_softirq_pending 202" and
>> I think it's related to mentioned commit (didn't bisect it yet).
>> See log from suspending.
>>
>> I have no reason to think the fix is wrong, it may just have revealed
>> another issue which existed before and was hidden by the bug.
>>
>> Rgds, Heiner
>>
>> [   75.073353] random: crng init done
>> [   75.073402] random: 7 urandom warning(s) missed due to ratelimiting
>> [   78.619564] PM: suspend entry (deep)
>> [   78.619675] PM: Syncing filesystems ... done.
>> [   78.653684] Freezing user space processes ... (elapsed 0.002 seconds) done.
>> [   78.656094] OOM killer disabled.
>> [   78.656113] Freezing remaining freezable tasks ... (elapsed 0.001 seconds) done.
>> [   78.658177] Suspending console(s) (use no_console_suspend to debug)
>> [   78.663066] nuvoton-cir 00:07: disabled
>> [   78.671817] sd 0:0:0:0: [sda] Synchronizing SCSI cache
>> [   78.672210] sd 0:0:0:0: [sda] Stopping disk
>> [   78.786651] ACPI: Preparing to enter system sleep state S3
>> [   78.789613] PM: Saving platform NVS memory
>> [   78.789759] Disabling non-boot CPUs ...
>> [   78.805154] NOHZ: local_softirq_pending 202
>> [   78.805182] NOHZ: local_softirq_pending 202
>> [   78.807102] smpboot: CPU 1 is now offline
> 
> I've tried to reproduce with suspend on disk but got unsuccessful.
> 
> A small question as I see someone is having a similar issue with a stable
> release only. On which kernel did you trigger that: upstream or stable?
> 
> I'll continue investigating.
> 
> Thanks.
> 
Affected is recent linux-next, after the commit mentioned in the subject.
I can work around the warning (not sure whether it's a proper fix),
see here:
https://lkml.org/lkml/2018/8/18/272

Rgds, Heiner