From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750939AbaIFBFf (ORCPT ); Fri, 5 Sep 2014 21:05:35 -0400 Received: from qmta05.emeryville.ca.mail.comcast.net ([76.96.30.48]:55696 "EHLO qmta05.emeryville.ca.mail.comcast.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750762AbaIFBFc (ORCPT ); Fri, 5 Sep 2014 21:05:32 -0400 Date: Thu, 4 Sep 2014 10:18:31 -0500 (CDT) From: Christoph Lameter X-X-Sender: cl@gentwo.org To: "Paul E. McKenney" cc: Frederic Weisbecker , linux-kernel@vger.kernel.org Subject: dynticks: Remove atomic ops for dynticks_idle Message-ID: Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This is on top of the first patch (but still not against your tree). I wonder what you think about this one. No special operations. Since dynticks_idle is only ever modified by the local cpu we do not need to use atomics there. Signed-off-by: Christoph Lameter Index: linux/kernel/rcu/tree.c =================================================================== --- linux.orig/kernel/rcu/tree.c +++ linux/kernel/rcu/tree.c @@ -213,7 +213,7 @@ static DEFINE_PER_CPU(struct rcu_dyntick .dynticks = ATOMIC_INIT(1), #ifdef CONFIG_NO_HZ_FULL_SYSIDLE .dynticks_idle_nesting = DYNTICK_TASK_NEST_VALUE, - .dynticks_idle = ATOMIC_INIT(1), + .dynticks_idle = 1, #endif /* #ifdef CONFIG_NO_HZ_FULL_SYSIDLE */ }; Index: linux/kernel/rcu/tree.h =================================================================== --- linux.orig/kernel/rcu/tree.h +++ linux/kernel/rcu/tree.h @@ -91,7 +91,7 @@ struct rcu_dynticks { #ifdef CONFIG_NO_HZ_FULL_SYSIDLE long long dynticks_idle_nesting; /* irq/process nesting level from idle. */ - atomic_t dynticks_idle; /* Even value for idle, else odd. */ + long dynticks_idle; /* Even value for idle, else odd. */ /* "Idle" excludes userspace execution. */ unsigned long dynticks_idle_jiffies; /* End of last non-NMI non-idle period. */ Index: linux/kernel/rcu/tree_plugin.h =================================================================== --- linux.orig/kernel/rcu/tree_plugin.h +++ linux/kernel/rcu/tree_plugin.h @@ -2644,9 +2644,9 @@ static void rcu_sysidle_enter(int irq) j = jiffies; ACCESS_ONCE(rdtp->dynticks_idle_jiffies) = j; smp_mb__before_atomic(); - atomic_inc(&rdtp->dynticks_idle); + rdtp->dynticks_idle++; smp_mb__after_atomic(); - WARN_ON_ONCE(atomic_read(&rdtp->dynticks_idle) & 0x1); + WARN_ON_ONCE(rdtp->dynticks_idle & 0x1); } /* @@ -2712,9 +2712,9 @@ static void rcu_sysidle_exit(int irq) /* Record end of idle period. */ smp_mb__before_atomic(); - atomic_inc(&rdtp->dynticks_idle); + rdtp->dynticks_idle++; smp_mb__after_atomic(); - WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks_idle) & 0x1)); + WARN_ON_ONCE(!(rdtp->dynticks_idle & 0x1)); /* * If we are the timekeeping CPU, we are permitted to be non-idle @@ -2755,7 +2755,7 @@ static void rcu_sysidle_check_cpu(struct WARN_ON_ONCE(smp_processor_id() != tick_do_timer_cpu); /* Pick up current idle and NMI-nesting counter and check. */ - cur = atomic_read(&rdtp->dynticks_idle); + cur = rdtp->dynticks_idle; if (cur & 0x1) { *isidle = false; /* We are not idle! */ return;