linux-kernel - Re: [PATCH tip/core/rcu 14/14] rcu: Fix rcu_is_cpu_idle() #ifdef in TINY

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Message-ID: <20120615225749.GQ2389@linux.vnet.ibm.com>
Date:	Fri, 15 Jun 2012 15:57:49 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Josh Triplett <josh@...htriplett.org>
Cc:	linux-kernel@...r.kernel.org, mingo@...e.hu, laijs@...fujitsu.com,
	dipankar@...ibm.com, akpm@...ux-foundation.org,
	mathieu.desnoyers@...ymtl.ca, 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,
	fweisbec@...il.com, patches@...aro.org,
	"Paul E. McKenney" <paul.mckenney@...aro.org>
Subject: Re: [PATCH tip/core/rcu 14/14] rcu: Fix rcu_is_cpu_idle() #ifdef in
 TINY_RCU

On Fri, Jun 15, 2012 at 02:28:28PM -0700, Josh Triplett wrote:
> On Fri, Jun 15, 2012 at 01:13:15PM -0700, Paul E. McKenney wrote:
> > From: "Paul E. McKenney" <paul.mckenney@...aro.org>
> > 
> > The rcu_is_cpu_idle() function is used if CONFIG_DEBUG_LOCK_ALLOC,
> > but TINY_RCU defines it only when CONFIG_PROVE_RCU.  This causes
> > build failures when CONFIG_DEBUG_LOCK_ALLOC=y but CONFIG_PROVE_RCU=n.
> > This commit therefore adjusts the #ifdefs for rcu_is_cpu_idle() so
> > that it is defined when CONFIG_DEBUG_LOCK_ALLOC=y.
> > 
> > Signed-off-by: Paul E. McKenney <paul.mckenney@...aro.org>
> > Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
> 
> Given that an earlier patch in this series makes rcupdate.h
> unconditionally prototype rcu_is_cpu_idle, shouldn't rcutiny.c define it
> unconditionally?  (And do so before the earlier patch in this series
> makes it available unconditionally?)

Or update that earlier patch so that it keeps rcu_is_cpu_idle() under
#ifdef CONFIG_DEBUG_LOCK_ALLOC.  Either way, good catch!

Hmmm...  I want it under CONFIG_DEBUG_LOCK_ALLOC for TINY_RCU (memory
footprint and all that), but unconditional for TREE_RCU.  That can
be arranged...

						Thanx, Paul

> - Josh Triplett
> 
> >  kernel/rcutiny.c |    4 ++--
> >  1 files changed, 2 insertions(+), 2 deletions(-)
> > 
> > diff --git a/kernel/rcutiny.c b/kernel/rcutiny.c
> > index 37a5444..547b1fe 100644
> > --- a/kernel/rcutiny.c
> > +++ b/kernel/rcutiny.c
> > @@ -172,7 +172,7 @@ void rcu_irq_enter(void)
> >  	local_irq_restore(flags);
> >  }
> >  
> > -#ifdef CONFIG_PROVE_RCU
> > +#ifdef CONFIG_DEBUG_LOCK_ALLOC
> >  
> >  /*
> >   * Test whether RCU thinks that the current CPU is idle.
> > @@ -183,7 +183,7 @@ int rcu_is_cpu_idle(void)
> >  }
> >  EXPORT_SYMBOL(rcu_is_cpu_idle);
> >  
> > -#endif /* #ifdef CONFIG_PROVE_RCU */
> > +#endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
> >  
> >  /*
> >   * Test whether the current CPU was interrupted from idle.  Nested
> > -- 
> > 1.7.8
> > 
> 

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