From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753304AbbBKQNi (ORCPT ); Wed, 11 Feb 2015 11:13:38 -0500 Received: from e34.co.us.ibm.com ([32.97.110.152]:57729 "EHLO e34.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752836AbbBKQNg (ORCPT ); Wed, 11 Feb 2015 11:13:36 -0500 Date: Wed, 11 Feb 2015 08:13:30 -0800 From: "Paul E. McKenney" To: Alexander Gordeev Cc: linux-kernel@vger.kernel.org Subject: Re: [PATCH 3/3] rcu: Call trace_rcu_batch_start() with enabled interrupts Message-ID: <20150211161330.GH4166@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 15021116-0017-0000-0000-000008A5A1AB Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Feb 11, 2015 at 03:42:39PM +0100, Alexander Gordeev wrote: > Currently trace_rcu_batch_start() is called with local > interrupts disabled. Yet, there is no reason to do so. > > Cc: "Paul E. McKenney" > Signed-off-by: Alexander Gordeev Hmmm... I am not seeing this one. As you noted in the commit log for your earlier patch, the purpose of Tiny RCU is to be tiny, not to be all that fast. This commit increases the size a bit (admittedly only when CONFIG_RCU_TRACE=y), and also increases complexity a bit. So it does not look to me to be something we want for Tiny RCU. So what am I missing here? Thanx, Paul > --- > kernel/rcu/tiny.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/kernel/rcu/tiny.c b/kernel/rcu/tiny.c > index 069742d..01e80ac 100644 > --- a/kernel/rcu/tiny.c > +++ b/kernel/rcu/tiny.c > @@ -166,11 +166,12 @@ static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp) > const char *rn = NULL; > struct rcu_head *next, *list; > unsigned long flags; > + RCU_TRACE(long qlen); > RCU_TRACE(int cb_count = 0); > > /* Move the ready-to-invoke callbacks to a local list. */ > local_irq_save(flags); > - RCU_TRACE(trace_rcu_batch_start(rcp->name, 0, rcp->qlen, -1)); > + RCU_TRACE(qlen = rcp->qlen); > list = rcp->rcucblist; > rcp->rcucblist = *rcp->donetail; > *rcp->donetail = NULL; > @@ -180,6 +181,7 @@ static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp) > local_irq_restore(flags); > > /* Invoke the callbacks on the local list. */ > + RCU_TRACE(trace_rcu_batch_start(rcp->name, 0, qlen, -1)); > RCU_TRACE(rn = rcp->name); > while (list) { > next = list->next; > -- > 1.8.3.1 >