Re: [RFC PATCH 00/12] locking/lockdep: Add a new class of terminal locks

Waiman Long
2018-11-10T23:36:03Z

On 11/10/2018 09:10 AM, Peter Zijlstra wrote:
> On Fri, Nov 09, 2018 at 09:04:12AM +0100, Ingo Molnar wrote:
>> BTW., if you are interested in more radical approaches to optimize
>> lockdep, we could also add a static checker via objtool driven call graph
>> analysis, and mark those locks terminal that we can prove are terminal.
>>
>> This would require the unified call graph of the kernel image and of all
>> modules to be examined in a final pass, but that's within the principal
>> scope of objtool. (This 'final pass' could also be done during bootup, at
>> least in initial versions.)
> Something like this is needed for objtool LTO support as well. I just
> dread the build time 'regressions' this will introduce :/
>
> The final link pass is already by far the most expensive part (as
> measured in wall-time) of building a kernel, adding more work there
> would really suck :/

I think the idea is to make objtool have the capability to do that. It
doesn't mean we need to turn it on by default in every build.

Cheers,
Longman