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

From: Frederic Weisbecker
Date: Fri Aug 24 2018 - 00:13:12 EST


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.