Re: [Ksummit-discuss] [MAINTAINERS SUMMIT] & [TECH TOPIC] Improve regression tracking

[James Bottomley <James.Bottomley@HansenPartnership.com>]

On Wed, 2017-07-05 at 11:20 -0400, Steven Rostedt wrote:
> On Wed, 05 Jul 2017 08:09:49 -0700
> James Bottomley <James.Bottomley@HansenPartnership.com> wrote:
> 
>  
> > 
> > > 
> > > > 
> > > > you're protecting was accessed outside the lock, which is the
> > > > usual source of concurrency problems.  In other words lockdep
> > > > is useful but it's not a panacea.  
> > > 
> > > Still not an excuse to not have lockdep enabled during tests.  
> > 
> > OK, what makes you think lockdep isn't enabled?  Since Kconfig is
> > so complex, I usually use a distro config ... they have it enabled
> > (or at least openSUSE does), so it's enabled for everything I do.
> 
> openSuSE has it enabled? I hope not for its production config, as
> lockdep has a huge performance penalty.

Then, surely, it's the last thing we want when tracking down race
conditgions since it will alter timings dramatically.

> I'm thinking you don't have it enabled. What config are you looking
> at? The actual config that does the testing of locks is
> CONFIG_PROVE_LOCKING, which selects LOCKDEP to be compiled in.

This is what it has:

jejb@jarvis:~/git/linux-build> grep LOCKDEP /boot/config-4.4.73-18.17-default 
CONFIG_LOCKDEP_SUPPORT=y

James