From patchwork Sat May 11 14:19:08 2013 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Robin Holt X-Patchwork-Id: 2554071 Return-Path: X-Original-To: patchwork-linux-arm@patchwork.kernel.org Delivered-To: patchwork-process-083081@patchwork2.kernel.org Received: from casper.infradead.org (casper.infradead.org [85.118.1.10]) by patchwork2.kernel.org (Postfix) with ESMTP id 4DA66DF230 for ; Sat, 11 May 2013 14:21:39 +0000 (UTC) Received: from merlin.infradead.org ([2001:4978:20e::2]) by casper.infradead.org with esmtps (Exim 4.80.1 #2 (Red Hat Linux)) id 1UbAey-0005cA-2z; Sat, 11 May 2013 14:20:28 +0000 Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.80.1 #2 (Red Hat Linux)) id 1UbAej-00039D-NC; Sat, 11 May 2013 14:20:13 +0000 Received: from relay2.sgi.com ([192.48.179.30] helo=relay.sgi.com) by merlin.infradead.org with esmtp (Exim 4.80.1 #2 (Red Hat Linux)) id 1UbAeF-00033R-7Q for linux-arm-kernel@lists.infradead.org; Sat, 11 May 2013 14:19:45 +0000 Received: from estes.americas.sgi.com (estes.americas.sgi.com [128.162.236.10]) by relay2.corp.sgi.com (Postfix) with ESMTP id 2A652304064; Sat, 11 May 2013 07:19:22 -0700 (PDT) Received: from asylum.americas.sgi.com (asylum.americas.sgi.com [128.162.246.107]) by estes.americas.sgi.com (Postfix) with ESMTP id EB8E67003218; Sat, 11 May 2013 09:19:21 -0500 (CDT) Received: by asylum.americas.sgi.com (Postfix, from userid 1641) id E436C14976; Sat, 11 May 2013 09:19:21 -0500 (CDT) From: Robin Holt To: Andrew Morton Subject: [PATCH -v11 01/11] CPU hotplug: Provide a generic helper to disable/enable CPU hotplug Date: Sat, 11 May 2013 09:19:08 -0500 Message-Id: <1368281958-26695-2-git-send-email-holt@sgi.com> X-Mailer: git-send-email 1.8.2.1 In-Reply-To: <1368281958-26695-1-git-send-email-holt@sgi.com> References: <1368281958-26695-1-git-send-email-holt@sgi.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20130511_101943_405347_AAE6A278 X-CRM114-Status: GOOD ( 19.18 ) X-Spam-Score: -5.7 (-----) X-Spam-Report: SpamAssassin version 3.3.2 on merlin.infradead.org summary: Content analysis details: (-5.7 points) pts rule name description ---- ---------------------- -------------------------------------------------- -2.3 RCVD_IN_DNSWL_MED RBL: Sender listed at http://www.dnswl.org/, medium trust [192.48.179.30 listed in list.dnswl.org] -1.4 RP_MATCHES_RCVD Envelope sender domain matches handover relay domain -1.9 BAYES_00 BODY: Bayes spam probability is 0 to 1% [score: 0.0000] Cc: Russ Anderson , the arch/x86 maintainers , Linux Kernel Mailing List , stable@vger.kernel.org, Robin Holt , "Srivatsa S. Bhat" , "H. Peter Anvin" , Russell King , Guan Xuetao , Arm Mailing List X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org From: "Srivatsa S. Bhat" There are instances in the kernel where we would like to disable CPU hotplug (from sysfs) during some important operation. Today the freezer code depends on this and the code to do it was kinda tailor-made for that. Restructure the code and make it generic enough to be useful for other usecases too. Signed-off-by: Srivatsa S. Bhat Signed-off-by: Robin Holt To: Andrew Morton Cc: H. Peter Anvin Cc: Russ Anderson Cc: Robin Holt Cc: Russell King Cc: Guan Xuetao Cc: Linux Kernel Mailing List Cc: the arch/x86 maintainers Cc: Arm Mailing List Cc: --- include/linux/cpu.h | 4 ++++ kernel/cpu.c | 55 ++++++++++++++++++++++------------------------------- 2 files changed, 27 insertions(+), 32 deletions(-) diff --git a/include/linux/cpu.h b/include/linux/cpu.h index c6f6e08..9f3c7e8 100644 --- a/include/linux/cpu.h +++ b/include/linux/cpu.h @@ -175,6 +175,8 @@ extern struct bus_type cpu_subsys; extern void get_online_cpus(void); extern void put_online_cpus(void); +extern void cpu_hotplug_disable(void); +extern void cpu_hotplug_enable(void); #define hotcpu_notifier(fn, pri) cpu_notifier(fn, pri) #define register_hotcpu_notifier(nb) register_cpu_notifier(nb) #define unregister_hotcpu_notifier(nb) unregister_cpu_notifier(nb) @@ -198,6 +200,8 @@ static inline void cpu_hotplug_driver_unlock(void) #define get_online_cpus() do { } while (0) #define put_online_cpus() do { } while (0) +#define cpu_hotplug_disable() do { } while (0) +#define cpu_hotplug_enable() do { } while (0) #define hotcpu_notifier(fn, pri) do { (void)(fn); } while (0) /* These aren't inline functions due to a GCC bug. */ #define register_hotcpu_notifier(nb) ({ (void)(nb); 0; }) diff --git a/kernel/cpu.c b/kernel/cpu.c index b5e4ab2..198a388 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -133,6 +133,27 @@ static void cpu_hotplug_done(void) mutex_unlock(&cpu_hotplug.lock); } +/* + * Wait for currently running CPU hotplug operations to complete (if any) and + * disable future CPU hotplug (from sysfs). The 'cpu_add_remove_lock' protects + * the 'cpu_hotplug_disabled' flag. The same lock is also acquired by the + * hotplug path before performing hotplug operations. So acquiring that lock + * guarantees mutual exclusion from any currently running hotplug operations. + */ +void cpu_hotplug_disable(void) +{ + cpu_maps_update_begin(); + cpu_hotplug_disabled = 1; + cpu_maps_update_done(); +} + +void cpu_hotplug_enable(void) +{ + cpu_maps_update_begin(); + cpu_hotplug_disabled = 0; + cpu_maps_update_done(); +} + #else /* #if CONFIG_HOTPLUG_CPU */ static void cpu_hotplug_begin(void) {} static void cpu_hotplug_done(void) {} @@ -541,36 +562,6 @@ static int __init alloc_frozen_cpus(void) core_initcall(alloc_frozen_cpus); /* - * Prevent regular CPU hotplug from racing with the freezer, by disabling CPU - * hotplug when tasks are about to be frozen. Also, don't allow the freezer - * to continue until any currently running CPU hotplug operation gets - * completed. - * To modify the 'cpu_hotplug_disabled' flag, we need to acquire the - * 'cpu_add_remove_lock'. And this same lock is also taken by the regular - * CPU hotplug path and released only after it is complete. Thus, we - * (and hence the freezer) will block here until any currently running CPU - * hotplug operation gets completed. - */ -void cpu_hotplug_disable_before_freeze(void) -{ - cpu_maps_update_begin(); - cpu_hotplug_disabled = 1; - cpu_maps_update_done(); -} - - -/* - * When tasks have been thawed, re-enable regular CPU hotplug (which had been - * disabled while beginning to freeze tasks). - */ -void cpu_hotplug_enable_after_thaw(void) -{ - cpu_maps_update_begin(); - cpu_hotplug_disabled = 0; - cpu_maps_update_done(); -} - -/* * When callbacks for CPU hotplug notifications are being executed, we must * ensure that the state of the system with respect to the tasks being frozen * or not, as reported by the notification, remains unchanged *throughout the @@ -589,12 +580,12 @@ cpu_hotplug_pm_callback(struct notifier_block *nb, case PM_SUSPEND_PREPARE: case PM_HIBERNATION_PREPARE: - cpu_hotplug_disable_before_freeze(); + cpu_hotplug_disable(); break; case PM_POST_SUSPEND: case PM_POST_HIBERNATION: - cpu_hotplug_enable_after_thaw(); + cpu_hotplug_enable(); break; default: