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

Peter Zijlstra
2018-11-10T22:43:29Z

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 :/