From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756767Ab2D3UJX (ORCPT ); Mon, 30 Apr 2012 16:09:23 -0400 Received: from mail-yx0-f202.google.com ([209.85.213.202]:41431 "EHLO mail-yx0-f202.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756722Ab2D3UJU (ORCPT ); Mon, 30 Apr 2012 16:09:20 -0400 From: Colin Cross To: linux-kernel@vger.kernel.org Cc: linux-arm-kernel@lists.infradead.org, linux-pm@lists.linux-foundation.org, Kevin Hilman , Len Brown , Trinabh Gupta , Arjan van de Ven , Deepthi Dharwar , Greg Kroah-Hartman , Kay Sievers , Santosh Shilimkar , Daniel Lezcano , Amit Kucheria , Lorenzo Pieralisi , Arnd Bergmann , Russell King , Colin Cross Subject: [PATCHv3 4/5] cpuidle: coupled: add parallel barrier function Date: Mon, 30 Apr 2012 13:09:10 -0700 Message-Id: <1335816551-27756-5-git-send-email-ccross@android.com> X-Mailer: git-send-email 1.7.7.3 In-Reply-To: <1335816551-27756-1-git-send-email-ccross@android.com> References: <1335816551-27756-1-git-send-email-ccross@android.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Adds cpuidle_coupled_parallel_barrier, which can be used by coupled cpuidle state enter functions to handle resynchronization after determining if any cpu needs to abort. The normal use case will be: static bool abort_flag; static atomic_t abort_barrier; int arch_cpuidle_enter(struct cpuidle_device *dev, ...) { if (arch_turn_off_irq_controller()) { /* returns an error if an irq is pending and would be lost if idle continued and turned off power */ abort_flag = true; } cpuidle_coupled_parallel_barrier(dev, &abort_barrier); if (abort_flag) { /* One of the cpus didn't turn off it's irq controller */ arch_turn_on_irq_controller(); return -EINTR; } /* continue with idle */ ... } This will cause all cpus to abort idle together if one of them needs to abort. Reviewed-by: Santosh Shilimkar Tested-by: Santosh Shilimkar Reviewed-by: Kevin Hilman Tested-by: Kevin Hilman Signed-off-by: Colin Cross --- drivers/cpuidle/coupled.c | 37 +++++++++++++++++++++++++++++++++++++ include/linux/cpuidle.h | 4 ++++ 2 files changed, 41 insertions(+), 0 deletions(-) diff --git a/drivers/cpuidle/coupled.c b/drivers/cpuidle/coupled.c index d097826..242dc7c 100644 --- a/drivers/cpuidle/coupled.c +++ b/drivers/cpuidle/coupled.c @@ -134,6 +134,43 @@ struct cpuidle_coupled { static cpumask_t cpuidle_coupled_poked_mask; /** + * cpuidle_coupled_parallel_barrier - synchronize all online coupled cpus + * @dev: cpuidle_device of the calling cpu + * @a: atomic variable to hold the barrier + * + * No caller to this function will return from this function until all online + * cpus in the same coupled group have called this function. Once any caller + * has returned from this function, the barrier is immediately available for + * reuse. + * + * The atomic variable a must be initialized to 0 before any cpu calls + * this function, will be reset to 0 before any cpu returns from this function. + * + * Must only be called from within a coupled idle state handler + * (state.enter when state.flags has CPUIDLE_FLAG_COUPLED set). + * + * Provides full smp barrier semantics before and after calling. + */ +void cpuidle_coupled_parallel_barrier(struct cpuidle_device *dev, atomic_t *a) +{ + int n = atomic_read(&dev->coupled->alive_count); + + smp_mb__before_atomic_inc(); + atomic_inc(a); + + while (atomic_read(a) < n) + cpu_relax(); + + if (atomic_inc_return(a) == n * 2) { + atomic_set(a, 0); + return; + } + + while (atomic_read(a) > n) + cpu_relax(); +} + +/** * cpuidle_state_is_coupled - check if a state is part of a coupled set * @dev: struct cpuidle_device for the current cpu * @drv: struct cpuidle_driver for the platform diff --git a/include/linux/cpuidle.h b/include/linux/cpuidle.h index 6038448..5ab7183 100644 --- a/include/linux/cpuidle.h +++ b/include/linux/cpuidle.h @@ -183,6 +183,10 @@ static inline int cpuidle_wrap_enter(struct cpuidle_device *dev, #endif +#ifdef CONFIG_ARCH_NEEDS_CPU_IDLE_COUPLED +void cpuidle_coupled_parallel_barrier(struct cpuidle_device *dev, atomic_t *a); +#endif + /****************************** * CPUIDLE GOVERNOR INTERFACE * ******************************/ -- 1.7.7.3