Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752543Ab0BNRsH (ORCPT ); Sun, 14 Feb 2010 12:48:07 -0500 Received: from e6.ny.us.ibm.com ([32.97.182.146]:37069 "EHLO e6.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752520Ab0BNRsC (ORCPT ); Sun, 14 Feb 2010 12:48:02 -0500 Date: Sun, 14 Feb 2010 09:48:03 -0800 From: "Paul E. McKenney" To: Peter Zijlstra Cc: linux-kernel@vger.kernel.org, mingo@elte.hu, laijs@cn.fujitsu.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@polymtl.ca, josh@joshtriplett.org, dvhltc@us.ibm.com, niv@us.ibm.com, tglx@linutronix.de, rostedt@goodmis.org, Valdis.Kletnieks@vt.edu, dhowells@redhat.com Subject: Re: [PATCH tip/core/rcu 06/13] sched: use lockdep-based checking on rcu_dereference() Message-ID: <20100214174803.GN7084@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20100212000016.GA25781@linux.vnet.ibm.com> <1265932839-25899-6-git-send-email-paulmck@linux.vnet.ibm.com> <1266142332.5273.415.camel@laptop> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1266142332.5273.415.camel@laptop> User-Agent: Mutt/1.5.15+20070412 (2007-04-11) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2723 Lines: 72 On Sun, Feb 14, 2010 at 11:12:12AM +0100, Peter Zijlstra wrote: > On Thu, 2010-02-11 at 16:00 -0800, Paul E. McKenney wrote: > > + first = rcu_dereference_check(pid->tasks[type].first, rcu_read_lock_held() || lockdep_is_held(&tasklist_lock)); > > if (first) > > result = hlist_entry(first, struct task_struct, pids[(type)].node); > > } > > I've seen that particular combination a few times in this patch, would > it make sense to create rcu_dereference_task()? > > > diff --git a/kernel/sched.c b/kernel/sched.c > > index c535cc4..ad419d9 100644 > > --- a/kernel/sched.c > > +++ b/kernel/sched.c > > @@ -645,6 +645,11 @@ static inline int cpu_of(struct rq *rq) > > #endif > > } > > > > +#define for_each_domain_rd(p) \ > > + rcu_dereference_check((p), \ > > + rcu_read_lock_sched_held() || \ > > + lockdep_is_held(&sched_domains_mutex)) > > + > > Would rcu_dereference_rd() not be a better name? We are probably going to need per-subsystem name spaces, so how about rcu_dereference_check_sched_domain()? Again, if agreeable, will send updated patch stack. Thanx, Paul ------------------------------------------------------------------------ sched: better name for for_each_domain_rd As suggested by Peter Ziljstra, make better choice of name for for_each_domain_rd(), containing "rcu_dereference", given that it is but a wrapper for rcu_dereference_check(). The name rcu_dereference_check_sched_domain() does that and provides a separate per-subsystem name space. Signed-off-by: Paul E. McKenney --- diff --git a/kernel/sched.c b/kernel/sched.c index ad419d9..478fc7d 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -645,7 +645,7 @@ static inline int cpu_of(struct rq *rq) #endif } -#define for_each_domain_rd(p) \ +#define rcu_dereference_check_sched_domain(p) \ rcu_dereference_check((p), \ rcu_read_lock_sched_held() || \ lockdep_is_held(&sched_domains_mutex)) @@ -658,7 +658,7 @@ static inline int cpu_of(struct rq *rq) * preempt-disabled sections. */ #define for_each_domain(cpu, __sd) \ - for (__sd = for_each_domain_rd(cpu_rq(cpu)->sd); __sd; __sd = __sd->parent) + for (__sd = rcu_dereference_check_sched_domain(cpu_rq(cpu)->sd); __sd; __sd = __sd->parent) #define cpu_rq(cpu) (&per_cpu(runqueues, (cpu))) #define this_rq() (&__get_cpu_var(runqueues)) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/