Re: [PATCH 13/26] locking: Add non-fatal spin lock assert

[Peter Hurley]

On 09/04/2014 01:14 AM, Ingo Molnar wrote:
> 
> * Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
> 
>> On Wed, Sep 03, 2014 at 10:50:01AM -0400, Peter Hurley wrote:
>>> So a lockdep-only assert is unlikely to draw attention to existing bugs,
>>> especially in established drivers.
>>
>> By the same logic lockdep will not find locking errors in established
>> drivers.
> 
> Indeed, this patch is ill-advised in several ways:
> 
>   - it extends an API variant that we want to phase
> 
>   - emits a warning even if say lockdep has already emitted a
>     warning and locking state is not guaranteed to be consistent. 
> 
>   - makes the kernel more expensive once fully debugged, in that
>     non-fatal checks are unconditional.

Ok.

One thing: I'm not seeing how lockdep_assert_held() switches off once
the warning has been emitted? Is the caller expected to construct their
own _ONCE tags?

Regards,
Peter Hurley
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