Should I do anything about this warning?

Should I do anything about this warning?

[Sagar Padhye]

Hi,
I am new at kernel programming. I have written a driver for a custom device, running on arm board. It works well (for last few months).
I happen to look at kernel logs and I seen,

[231250.894334] ------------[ cut here ]------------
[231250.899146] WARNING: at kernel/workqueue.c:1953 process_one_work+0x398/0x52c()
[231250.906491] Modules linked in: bcmdhd cfg80211 <XYZ>
[231250.911885] [<c0016450>] (unwind_backtrace+0x0/0x144) from [<c05c04f0>] (dump_stack+0x20/0x24)
[231250.920672] [<c05c04f0>] (dump_stack+0x20/0x24) from [<c006c330>] (warn_slowpath_common+0x5c/0x74)
[231250.929757] [<c006c330>] (warn_slowpath_common+0x5c/0x74) from [<c006c374>] (warn_slowpath_null+0x2c/0x34)
[231250.939581] [<c006c374>] (warn_slowpath_null+0x2c/0x34) from [<c0088f08>] (process_one_work+0x398/0x52c)
[231250.949232] [<c0088f08>] (process_one_work+0x398/0x52c) from [<c00895c8>] (rescuer_thread+0x184/0x230)
[231250.958708] [<c00895c8>] (rescuer_thread+0x184/0x230) from [<c008dd60>] (kthread+0xac/0xb4)
[231250.967236] [<c008dd60>] (kthread+0xac/0xb4) from [<c000fd4c>] (kernel_thread_exit+0x0/0x8)
[231250.975755] ---[ end trace 9f9c2187c0bee21b ]---

The device is still working after this. No issues in operation. I am just sceptical about analyzing this issue? Do I need to check more? If yes how? with this trace?

Thanks,
Sagar

Should I do anything about this warning?

[Kristof Provost]

On 2014-10-08 12:43:58 (+0530), Sagar Padhye <sgr.m.pdy@gmail.com> wrote:
> I am new at kernel programming. I have written a driver for a custom
> device, running on arm board. It works well (for last few months).  I
> happen to look at kernel logs and I seen,
> 
> [231250.899146] WARNING: at kernel/workqueue.c:1953 process_one_work+0x398/0x52c()
> 
You triggered a warning in the code.

> The device is still working after this. No issues in operation. I am
> just sceptical about analyzing this issue? Do I need to check more? If
> yes how? with this trace?
> 
Yes, this indicates a potential problem.
You start my looking at line 1953 in kernel/workqueue.c, where you'll
see which specific warning you're triggering.

It's probably this one:
>   /* ensure we're on the correct CPU */
>    WARN_ON_ONCE(!(pool->flags & POOL_DISASSOCIATED) &&
>             raw_smp_processor_id() != pool->cpu);

Regards,
Kristof

Should I do anything about this warning?

[Sagar Padhye]

On Wed, Oct 08, 2014 at 11:33:57AM +0200, Kristof Provost wrote:
> On 2014-10-08 12:43:58 (+0530), Sagar Padhye <sgr.m.pdy@gmail.com> wrote:
> > I am new at kernel programming. I have written a driver for a custom
> > device, running on arm board. It works well (for last few months).  I
> > happen to look at kernel logs and I seen,
> > 
> > [231250.899146] WARNING: at kernel/workqueue.c:1953 process_one_work+0x398/0x52c()
> > 
> You triggered a warning in the code.
Yes, I got that

> > The device is still working after this. No issues in operation. I am
> > just sceptical about analyzing this issue? Do I need to check more? If
> > yes how? with this trace?
> > 
> Yes, this indicates a potential problem.
The issue is not reproducible. Haven't seen in over 6 months. And the module is working just fine after the log.
Is there a way I can get more info on this e.g. more stacktrace that will end up in module's work function (if this occurs again)?
> You start my looking at line 1953 in kernel/workqueue.c, where you'll
> see which specific warning you're triggering.
> 
> It's probably this one:
> >   /* ensure we're on the correct CPU */
> >    WARN_ON_ONCE(!(pool->flags & POOL_DISASSOCIATED) &&
> >             raw_smp_processor_id() != pool->cpu);
They are,
1952 WARN_ON_ONCE(!(worker->flags & (WORKER_UNBOUND | WORKER_REBIND)) &&
1953      raw_smp_processor_id() != gcwq->cpu);
But I am not sure what they signify :(

Thanks,
Sagar