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Date: Sat, 11 Apr 2009 03:15:06 +0200
From: Frederic Weisbecker <fweisbec@gmail.com>
To: Ingo Molnar <mingo@elte.hu>
Cc: Greg KH <gregkh@suse.de>, LKML <linux-kernel@vger.kernel.org>,
       LTP <ltp-list@lists.sourceforge.net>,
       Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH 2/2] lockdep: choose to continue lock debugging despite
	taint
Message-ID: <20090411011505.GA5992@nowhere>
References: <1239312460-13396-1-git-send-email-fweisbec@gmail.com> <1239312460-13396-2-git-send-email-fweisbec@gmail.com> <20090410121515.GP21506@elte.hu> <20090410133844.GD5988@nowhere> <20090410134520.GC17878@elte.hu>
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On Fri, Apr 10, 2009 at 03:45:20PM +0200, Ingo Molnar wrote:
> 
> * Frederic Weisbecker <fweisbec@gmail.com> wrote:
> 
> > On Fri, Apr 10, 2009 at 02:15:15PM +0200, Ingo Molnar wrote:
> > > 
> > > * Frederic Weisbecker <fweisbec@gmail.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?
> 
> We can exclude TAINT_WARN too - i.e. (TAINT_CRAP|TAINT_WARN).
> 
> 	Ingo


Fine :-)

See the v2 on further mails in this thread.

Side request: do you think you could merge them on kill-the-BKL tree?

Thanks!