linux-kernel - Re: [RFC/INCOMPLETE 01/13] context_tracking: Add context_tracking_assert

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Message-ID: <20150618095955.GB4528@gmail.com>
Date:	Thu, 18 Jun 2015 11:59:55 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:	Andy Lutomirski <luto@...nel.org>, x86@...nel.org,
	linux-kernel@...r.kernel.org,
	Frédéric Weisbecker <fweisbec@...il.com>,
	Rik van Riel <riel@...hat.com>,
	Oleg Nesterov <oleg@...hat.com>,
	Denys Vlasenko <vda.linux@...glemail.com>,
	Borislav Petkov <bp@...en8.de>,
	Kees Cook <keescook@...omium.org>,
	Brian Gerst <brgerst@...il.com>
Subject: Re: [RFC/INCOMPLETE 01/13] context_tracking: Add
 context_tracking_assert_state


* Paul E. McKenney <paulmck@...ux.vnet.ibm.com> wrote:

> On Wed, Jun 17, 2015 at 11:41:14AM +0200, Ingo Molnar wrote:
> > 
> > * Andy Lutomirski <luto@...nel.org> wrote:
> > 
> > > This will let us sprinkle sanity checks around the kernel without
> > > making too much of a mess.
> > > 
> > > Signed-off-by: Andy Lutomirski <luto@...nel.org>
> > > ---
> > >  include/linux/context_tracking.h | 8 ++++++++
> > >  1 file changed, 8 insertions(+)
> > > 
> > > diff --git a/include/linux/context_tracking.h b/include/linux/context_tracking.h
> > > index 2821838256b4..0fbea4b152e1 100644
> > > --- a/include/linux/context_tracking.h
> > > +++ b/include/linux/context_tracking.h
> > > @@ -57,6 +57,13 @@ static inline void context_tracking_task_switch(struct task_struct *prev,
> > >  	if (context_tracking_is_enabled())
> > >  		__context_tracking_task_switch(prev, next);
> > >  }
> > > +
> > > +static inline void context_tracking_assert_state(enum ctx_state state)
> > > +{
> > > +	rcu_lockdep_assert(!context_tracking_is_enabled() ||
> > > +			   this_cpu_read(context_tracking.state) == state,
> > > +			   "context tracking state was wrong");
> > > +}
> > 
> > Please don't introduce assert() style debug check interfaces!
> > 
> > (And RCU should be fixed too I suspect.)
> 
> The thought is to rename rcu_lockdep_assert() to RCU_LOCKDEP_WARN()
> by analogy to WARN()?  Easy to do if so!  Or am I missing the point?

Yeah, and inverting the condition. Assuming the condition was assert()-style 
inverted to begin with! :-)

and lockdep should be fixed too I suspect, lockdep_assert_held() was really a 
poorly chosen name I suspect, it should be 'lockdep_check_held()' or so? It has 
very little to do with the assert() interface.

Thanks,

	Ingo
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