Re: linux-next: Tree for Feb 4

Sedat Dilek
2015-02-05T14:57:16Z

On Thu, Feb 5, 2015 at 8:14 AM, Dave Hansen <dave@sr71.net> wrote:
> On 02/04/2015 05:53 PM, Sedat Dilek wrote:
>> The architecture-specific switch_mm() function can be called by offline
>> CPUs, but includes event tracing, which cannot be legally carried out
>> on offline CPUs. This results in a lockdep-RCU splat. This commit fixes
>> this splat by omitting the tracing when the CPU is offline.
> ...
>>>> >> > load_cr3(next->pgd);
>>>> >> > - trace_tlb_flush(TLB_FLUSH_ON_TASK_SWITCH, TLB_FLUSH_ALL);
>>>> >> > + if (cpu_online(smp_processor_id()))
>>>> >> > + trace_tlb_flush(TLB_FLUSH_ON_TASK_SWITCH, TLB_FLUSH_ALL);
>
> Is this, perhaps, something that we should be doing in the generic trace
> code so that all of the trace users don't have to worry about it? Also,
> this patch will add overhead to the code when tracing is off. It would
> be best if we could manage to make the cpu_online() check only in the
> cases where the tracepoint is on.

Hi Dave,

thanks for your feedback.

I have just seen that I again see the call-trace.

Maybe you can discuss with Paul and others or offer a proposal patch.

I should really do something for my recovery (influenza).
Instead of laying lazy in my bed I thought to update my Linux kernels
and graphics driver stack which made me happy.

Regards,
- Sedat -