From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755470Ab0AMK2G (ORCPT ); Wed, 13 Jan 2010 05:28:06 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755505Ab0AMK2C (ORCPT ); Wed, 13 Jan 2010 05:28:02 -0500 Received: from hera.kernel.org ([140.211.167.34]:58714 "EHLO hera.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755464Ab0AMK2A (ORCPT ); Wed, 13 Jan 2010 05:28:00 -0500 Date: Wed, 13 Jan 2010 10:27:11 GMT From: "tip-bot for Paul E. McKenney" Cc: linux-kernel@vger.kernel.org, paulmck@linux.vnet.ibm.com, hpa@zytor.com, mingo@redhat.com, tglx@linutronix.de, mingo@elte.hu Reply-To: mingo@redhat.com, hpa@zytor.com, paulmck@linux.vnet.ibm.com, linux-kernel@vger.kernel.org, tglx@linutronix.de, mingo@elte.hu In-Reply-To: <12626465501854-git-send-email-> References: <12626465501854-git-send-email-> To: linux-tip-commits@vger.kernel.org Subject: [tip:core/rcu] rcu: Make force_quiescent_state() start grace period if needed Message-ID: Git-Commit-ID: 46a1e34eda805501a8b32f26394faa435149f6d1 X-Mailer: tip-git-log-daemon MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.2.3 (hera.kernel.org [127.0.0.1]); Wed, 13 Jan 2010 10:27:12 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 46a1e34eda805501a8b32f26394faa435149f6d1 Gitweb: http://git.kernel.org/tip/46a1e34eda805501a8b32f26394faa435149f6d1 Author: Paul E. McKenney AuthorDate: Mon, 4 Jan 2010 15:09:09 -0800 Committer: Ingo Molnar CommitDate: Wed, 13 Jan 2010 09:06:05 +0100 rcu: Make force_quiescent_state() start grace period if needed Grace periods cannot be started while force_quiescent_state() is active. This is OK in that the affected CPUs will try again later, but it does induce needless grace-period delays. This patch causes rcu_start_gp() to record a failed attempt to start a grace period. When force_quiescent_state() prepares to return, it then starts the grace period if there was such a failed attempt. Signed-off-by: Paul E. McKenney Cc: laijs@cn.fujitsu.com Cc: dipankar@in.ibm.com Cc: mathieu.desnoyers@polymtl.ca Cc: josh@joshtriplett.org Cc: dvhltc@us.ibm.com Cc: niv@us.ibm.com Cc: peterz@infradead.org Cc: rostedt@goodmis.org Cc: Valdis.Kletnieks@vt.edu Cc: dhowells@redhat.com LKML-Reference: <12626465501854-git-send-email-> Signed-off-by: Ingo Molnar --- kernel/rcutree.c | 8 ++++++++ kernel/rcutree.h | 5 +++++ 2 files changed, 13 insertions(+), 0 deletions(-) diff --git a/kernel/rcutree.c b/kernel/rcutree.c index d920285..55e8f6e 100644 --- a/kernel/rcutree.c +++ b/kernel/rcutree.c @@ -660,6 +660,8 @@ rcu_start_gp(struct rcu_state *rsp, unsigned long flags) struct rcu_node *rnp = rcu_get_root(rsp); if (!cpu_needs_another_gp(rsp, rdp) || rsp->fqs_active) { + if (cpu_needs_another_gp(rsp, rdp)) + rsp->fqs_need_gp = 1; if (rnp->completed == rsp->completed) { spin_unlock_irqrestore(&rnp->lock, flags); return; @@ -1239,6 +1241,12 @@ static void force_quiescent_state(struct rcu_state *rsp, int relaxed) break; } rsp->fqs_active = 0; + if (rsp->fqs_need_gp) { + spin_unlock(&rsp->fqslock); /* irqs remain disabled */ + rsp->fqs_need_gp = 0; + rcu_start_gp(rsp, flags); /* releases rnp->lock */ + return; + } spin_unlock(&rnp->lock); /* irqs remain disabled */ unlock_fqs_ret: spin_unlock_irqrestore(&rsp->fqslock, flags); diff --git a/kernel/rcutree.h b/kernel/rcutree.h index edb6fae..bd5d78a 100644 --- a/kernel/rcutree.h +++ b/kernel/rcutree.h @@ -278,6 +278,11 @@ struct rcu_state { /* Force QS state. */ u8 fqs_active; /* force_quiescent_state() */ /* is running. */ + u8 fqs_need_gp; /* A CPU was prevented from */ + /* starting a new grace */ + /* period because */ + /* force_quiescent_state() */ + /* was running. */ long gpnum; /* Current gp number. */ long completed; /* # of last completed gp. */