linux-kernel - Re: [PATCH v3] rcu: define tracepoint strings only if CONFIG

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Date:	Wed, 16 Jul 2014 04:55:04 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Ard Biesheuvel <ard.biesheuvel@...aro.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] rcu: define tracepoint strings only if CONFIG_TRACING
 is set

On Mon, Jul 14, 2014 at 01:03:02PM -0400, Steven Rostedt wrote:
> On Sat, 12 Jul 2014 19:01:49 +0200
> Ard Biesheuvel <ard.biesheuvel@...aro.org> wrote:
> 
> > Commit f7f7bac9cb1c ("rcu: Have the RCU tracepoints use the tracepoint_string
> > infrastructure") unconditionally populates the __tracepoint_str input section,
> > but this section is not assigned an output section if CONFIG_TRACING is not set.
> > This results in the __tracepoint_str turning up in unexpected places, i.e.,
> > after _edata.
> > 
> > Signed-off-by: Ard Biesheuvel <ard.biesheuvel@...aro.org>
> > Cc: rostedt@...dmis.org
> > Cc: paulmck@...ux.vnet.ibm.com
> > ---
> > v3:
> > - make definition of <var>_varname conditional as well
> > v2:
> > - s/DEFINE_TPS/DEFINE_RCU_TPS/
> > 
> >  kernel/rcu/tree.c | 15 ++++++++++++---
> >  1 file changed, 12 insertions(+), 3 deletions(-)
> > 
> 
> Reviewed-by: Steven Rostedt <rostedt@...dmis.org>

Queued for 3.18, thank you both!

							Thanx, Paul

> -- Steve
> 
> > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> > index f1ba77363fbb..0756a4696007 100644
> > --- a/kernel/rcu/tree.c
> > +++ b/kernel/rcu/tree.c
> > @@ -79,9 +79,18 @@ static struct lock_class_key rcu_fqs_class[RCU_NUM_LVLS];
> >   * the tracing userspace tools to be able to decipher the string
> >   * address to the matching string.
> >   */
> > -#define RCU_STATE_INITIALIZER(sname, sabbr, cr) \
> > +#ifdef CONFIG_TRACING
> > +# define DEFINE_RCU_TPS(sname) \
> >  static char sname##_varname[] = #sname; \
> > -static const char *tp_##sname##_varname __used __tracepoint_string = sname##_varname; \
> > +static const char *tp_##sname##_varname __used __tracepoint_string = sname##_varname;
> > +# define RCU_STATE_NAME(sname) sname##_varname
> > +#else
> > +# define DEFINE_RCU_TPS(sname)
> > +# define RCU_STATE_NAME(sname) __stringify(sname)
> > +#endif
> > +
> > +#define RCU_STATE_INITIALIZER(sname, sabbr, cr) \
> > +DEFINE_RCU_TPS(sname) \
> >  struct rcu_state sname##_state = { \
> >  	.level = { &sname##_state.node[0] }, \
> >  	.call = cr, \
> > @@ -93,7 +102,7 @@ struct rcu_state sname##_state = { \
> >  	.orphan_donetail = &sname##_state.orphan_donelist, \
> >  	.barrier_mutex = __MUTEX_INITIALIZER(sname##_state.barrier_mutex), \
> >  	.onoff_mutex = __MUTEX_INITIALIZER(sname##_state.onoff_mutex), \
> > -	.name = sname##_varname, \
> > +	.name = RCU_STATE_NAME(sname), \
> >  	.abbr = sabbr, \
> >  }; \
> >  DEFINE_PER_CPU(struct rcu_data, sname##_data)
> 

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