From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753442Ab2H3VQ4 (ORCPT ); Thu, 30 Aug 2012 17:16:56 -0400 Received: from e36.co.us.ibm.com ([32.97.110.154]:47656 "EHLO e36.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753062Ab2H3VOX (ORCPT ); Thu, 30 Aug 2012 17:14:23 -0400 From: "Paul E. McKenney" To: linux-kernel@vger.kernel.org Cc: 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, peterz@infradead.org, 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, Richard Henderson , Ivan Kokshaysky , Matt Turner , alpha , "Paul E. McKenney" , Michael Cree , "3.2.x.." Subject: [PATCH tip/core/rcu 16/26] alpha: Add missing RCU idle APIs on idle loop Date: Thu, 30 Aug 2012 14:05:33 -0700 Message-Id: <1346360743-3628-16-git-send-email-paulmck@linux.vnet.ibm.com> X-Mailer: git-send-email 1.7.8 In-Reply-To: <1346360743-3628-1-git-send-email-paulmck@linux.vnet.ibm.com> References: <20120830210520.GA2824@linux.vnet.ibm.com> <1346360743-3628-1-git-send-email-paulmck@linux.vnet.ibm.com> X-Content-Scanned: Fidelis XPS MAILER x-cbid: 12083021-7606-0000-0000-00000334D1C7 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Frederic Weisbecker 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: Michael Cree Cc: 3.2.x.. --- arch/alpha/kernel/process.c | 3 +++ 1 files changed, 3 insertions(+), 0 deletions(-) diff --git a/arch/alpha/kernel/process.c b/arch/alpha/kernel/process.c index eac5e01..eb9558c 100644 --- a/arch/alpha/kernel/process.c +++ b/arch/alpha/kernel/process.c @@ -28,6 +28,7 @@ #include #include #include +#include #include #include @@ -54,9 +55,11 @@ cpu_idle(void) /* FIXME -- EV6 and LCA45 know how to power down the CPU. */ + rcu_idle_enter(); while (!need_resched()) cpu_relax(); + rcu_idle_exit(); schedule_preempt_disabled(); } } -- 1.7.8