From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755207Ab2IFNd0 (ORCPT ); Thu, 6 Sep 2012 09:33:26 -0400 Received: from merlin.infradead.org ([205.233.59.134]:33973 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754590Ab2IFNdZ convert rfc822-to-8bit (ORCPT ); Thu, 6 Sep 2012 09:33:25 -0400 Message-ID: <1346938342.18408.3.camel@twins> Subject: Re: [PATCH tip/core/rcu 01/23] rcu: Move RCU grace-period initialization into a kthread From: Peter Zijlstra To: "Paul E. McKenney" 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, niv@us.ibm.com, tglx@linutronix.de, rostedt@goodmis.org, Valdis.Kletnieks@vt.edu, dhowells@redhat.com, eric.dumazet@gmail.com, darren@dvhart.com, fweisbec@gmail.com, sbw@mit.edu, patches@linaro.org Date: Thu, 06 Sep 2012 15:32:22 +0200 In-Reply-To: <1346350718-30937-1-git-send-email-paulmck@linux.vnet.ibm.com> References: <20120830181811.GA29154@linux.vnet.ibm.com> <1346350718-30937-1-git-send-email-paulmck@linux.vnet.ibm.com> Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7BIT X-Mailer: Evolution 3.2.2- Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2012-08-30 at 11:18 -0700, Paul E. McKenney wrote: > +static int rcu_gp_kthread(void *arg) > +{ > + unsigned long flags; > + struct rcu_data *rdp; > + struct rcu_node *rnp; > + struct rcu_state *rsp = arg; > + > + for (;;) { > + > + /* Handle grace-period start. */ > + rnp = rcu_get_root(rsp); > + for (;;) { > + wait_event_interruptible(rsp->gp_wq, rsp->gp_flags); > + if (rsp->gp_flags) > + break; > + flush_signals(current); > + } > + raw_spin_lock_irqsave(&rnp->lock, flags); You're in a kthread, it should be impossible for IRQs to be disabled here, no? Similar for most (all) other sites in this function. Using the unconditional IRQ disable/enable is generally faster.