linux-kernel - Re: [PATCH RFC tip/core/rcu 05/11] rcu: add comment saying why DEBUG_OBJECTS_RCU

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Message-ID: <BLU0-SMTP11F8F588EC47CF2C6BAA5896DB0@phx.gbl>
Date:	Wed, 23 Feb 2011 10:02:04 -0500
From:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
To:	Steven Rostedt <rostedt@...dmis.org>
CC:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	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, Valdis.Kletnieks@...edu, dhowells@...hat.com,
	eric.dumazet@...il.com, darren@...art.com
Subject: Re: [PATCH RFC tip/core/rcu 05/11] rcu: add comment saying why
	DEBUG_OBJECTS_RCU_HEAD depends on PREEMPT.

* Steven Rostedt (rostedt@...dmis.org) wrote:
> On Wed, 2011-02-23 at 08:59 -0500, Mathieu Desnoyers wrote:
> 
> > #ifdef CONFIG_PREEMPT
> >                 /*
> >                  * Ensure that queued callbacks are all executed.
> >                  * If we detect that we are nested in a RCU read-side
> >                  * critical
> >                  * section, we should simply fail, otherwise we would
> >                  * deadlock.
> >                  */
> >                 if (rcu_preempt_depth() != 0 || preempt_count() != 0 ||
> >                     irqs_disabled()) {
> >                         WARN_ON(1);
> >                         return 0;
> >                 }
> >                 rcu_barrier();
> >                 rcu_barrier_sched();
> >                 rcu_barrier_bh();
> >                 debug_object_init(head, &rcuhead_debug_descr);
> >                 return 1;
> > #else
> > 		return 0;
> > #endif
> > 
> > instead, no ?
> 
> BTW, if you do end up doing such a thing...
> 
> #ifndef CONFIG_PREEMPT
> 	return 0;
> #endif
> 
> before all that would be much cleaner.
> 
> Just make sure any non defined in PREEMPT macros/functions are defined
> as nops in !CONFIG_PREEMPT

Good point, thanks !

Mathieu

> 
> -- Steve
> 
> 

-- 
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com
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