linux-kernel - Re: [PATCH tip/core/rcu 07/28] Fix mismatched variable in rcutree

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Date:	Wed, 8 Jun 2011 17:03:48 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
Cc:	linux-kernel@...r.kernel.org, mingo@...e.hu, laijs@...fujitsu.com,
	dipankar@...ibm.com, akpm@...ux-foundation.org,
	josh@...htriplett.org, niv@...ibm.com, tglx@...utronix.de,
	peterz@...radead.org, rostedt@...dmis.org, Valdis.Kletnieks@...edu,
	dhowells@...hat.com, eric.dumazet@...il.com, darren@...art.com,
	patches@...aro.org, Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH tip/core/rcu 07/28] Fix mismatched variable in
 rcutree_trace.c

On Wed, Jun 08, 2011 at 07:23:29PM -0400, Mathieu Desnoyers wrote:
> * Paul E. McKenney (paulmck@...ux.vnet.ibm.com) wrote:
> > From: Andi Kleen <ak@...ux.intel.com>
> > 
> > rcutree.c defines rcu_cpu_kthread_cpu as int, not unsigned int,
> > so the extern has to follow that.
> 
> How comes this discrepancy was made possible in the first place ? This
> declaration should appear in a header included by both rcutree_trace.c
> and rcutree.c, which would have permitted the compiler to detect this.
> 
> Maybe kernel/rcutree.h would be a good location for these ?

I vaguely recall a time where this didn't work, but will give it
another try.  It would certainly be nicer if the compiler checked
for these sorts of mismatches!

							Thanx, Paul

> Mathieu
> 
> > 
> > Cc: paulmck@...ux.vnet.ibm.com
> > Signed-off-by: Andi Kleen <ak@...ux.intel.com>
> > Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
> > ---
> >  kernel/rcutree_trace.c |    2 +-
> >  1 files changed, 1 insertions(+), 1 deletions(-)
> > 
> > diff --git a/kernel/rcutree_trace.c b/kernel/rcutree_trace.c
> > index 9678cc3..91c56e5 100644
> > --- a/kernel/rcutree_trace.c
> > +++ b/kernel/rcutree_trace.c
> > @@ -47,7 +47,7 @@
> >  #include "rcutree.h"
> >  
> >  DECLARE_PER_CPU(unsigned int, rcu_cpu_kthread_status);
> > -DECLARE_PER_CPU(unsigned int, rcu_cpu_kthread_cpu);
> > +DECLARE_PER_CPU(int, rcu_cpu_kthread_cpu);
> >  DECLARE_PER_CPU(unsigned int, rcu_cpu_kthread_loops);
> >  DECLARE_PER_CPU(char, rcu_cpu_has_work);
> >  
> > -- 
> > 1.7.3.2
> > 
> 
> -- 
> Mathieu Desnoyers
> Operating System Efficiency R&D Consultant
> EfficiOS Inc.
> http://www.efficios.com
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