From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758174Ab2HVQYI (ORCPT ); Wed, 22 Aug 2012 12:24:08 -0400 Received: from mail-ey0-f174.google.com ([209.85.215.174]:36983 "EHLO mail-ey0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757918Ab2HVQYE (ORCPT ); Wed, 22 Aug 2012 12:24:04 -0400 From: Frederic Weisbecker To: LKML Cc: Frederic Weisbecker , Richard Henderson , Ivan Kokshaysky , Matt Turner , alpha , "Paul E. McKenney" , "3.2.x.." Subject: [PATCH 01/10] alpha: Add missing RCU idle APIs on idle loop Date: Wed, 22 Aug 2012 18:23:39 +0200 Message-Id: <1345652628-15060-2-git-send-email-fweisbec@gmail.com> X-Mailer: git-send-email 1.7.5.4 In-Reply-To: <1345652628-15060-1-git-send-email-fweisbec@gmail.com> References: <1345652628-15060-1-git-send-email-fweisbec@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org In the old times, the whole idle task was considered as an RCU quiescent state. But as RCU became more and more successful overtime, some RCU read side critical section have been added even in the code of some architectures idle tasks, for tracing for example. So nowadays, rcu_idle_enter() and rcu_idle_exit() must be called by the architecture to tell RCU about the part in the idle loop that doesn't make use of rcu read side critical sections, typically the part that puts the CPU in low power mode. This is necessary for RCU to find the quiescent states in idle in order to complete grace periods. Add this missing pair of calls in the Alpha's idle loop. Reported-by: Paul E. McKenney Signed-off-by: Frederic Weisbecker Cc: Richard Henderson Cc: Ivan Kokshaysky Cc: Matt Turner Cc: alpha Cc: Paul E. McKenney Cc: 3.2.x.. --- arch/alpha/kernel/process.c | 6 +++++- 1 files changed, 5 insertions(+), 1 deletions(-) diff --git a/arch/alpha/kernel/process.c b/arch/alpha/kernel/process.c index 153d3fc..2ebf7b5 100644 --- a/arch/alpha/kernel/process.c +++ b/arch/alpha/kernel/process.c @@ -28,6 +28,7 @@ #include #include #include +#include #include #include @@ -50,13 +51,16 @@ cpu_idle(void) { set_thread_flag(TIF_POLLING_NRFLAG); + preempt_disable(); while (1) { /* FIXME -- EV6 and LCA45 know how to power down the CPU. */ + rcu_idle_enter(); while (!need_resched()) cpu_relax(); - schedule(); + rcu_idle_exit(); + schedule_preempt_disabled(); } } -- 1.7.5.4