linux-kernel - Re: [PATCH 2/2] lockdep: choose to continue lock debugging despite taint

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Date:	Fri, 10 Apr 2009 15:38:45 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Greg KH <gregkh@...e.de>, LKML <linux-kernel@...r.kernel.org>,
	LTP <ltp-list@...ts.sourceforge.net>,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH 2/2] lockdep: choose to continue lock debugging despite
	taint

On Fri, Apr 10, 2009 at 02:15:15PM +0200, Ingo Molnar wrote:
> 
> * Frederic Weisbecker <fweisbec@...il.com> wrote:
> 
> > Lockdep is disabled after any kernel taints. This might be 
> > convenient to ignore bad locking issues which sources come from 
> > outside the kernel tree. Nevertheless, it might be a frustrating 
> > experience for the staging developers or anyone who might develop 
> > a kernel that happens to be tainted.
> 
> Good point. Not having lockdep coverage for drivers/staging/ just 
> prolongs their transition - not good.
> 
> But instead of this:
> 
> >  void add_taint(unsigned flag)
> >  {
> > +#ifndef CONFIG_LOCKDEP_IGNORE_TAINT
> >  	/*
> >  	 * Can't trust the integrity of the kernel anymore.
> >  	 * We don't call directly debug_locks_off() because the issue
> > @@ -220,6 +221,7 @@ void add_taint(unsigned flag)
> >  	 */
> >  	if (xchg(&debug_locks, 0))
> >  		printk(KERN_WARNING "Disabling lockdep due to kernel taint\n");
> > +#endif
> 
> I'd suggest to not do the debug_locks_off() call if TAINT_CRAP. I.e. 
> something like:
> 
> 	if (!(flag & TAINT_CRAP) && debug_locks_off())
> 		printk(...);
> 
> will do the trick.
> 
> 	Ingo


Ok, but this is not only about staging. It's also about TAINT_WARN.
Just imagine that you report a warning to a maintainer, and while
you are waiting for it to be fixed, you can't use lockdep for your
own needs.

Hm?

Frederic.

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