From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752943AbbD3Tjl (ORCPT ); Thu, 30 Apr 2015 15:39:41 -0400 Received: from mail-db3on0090.outbound.protection.outlook.com ([157.55.234.90]:47552 "EHLO emea01-db3-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752899AbbD3Tjf (ORCPT ); Thu, 30 Apr 2015 15:39:35 -0400 Authentication-Results: spf=fail (sender IP is 12.216.194.146) smtp.mailfrom=ezchip.com; ezchip.com; dkim=none (message not signed) header.d=none; From: Chris Metcalf To: Frederic Weisbecker , Don Zickus , Ingo Molnar , Andrew Morton , Andrew Jones , chai wen , Ulrich Obergfell , Fabian Frederick , Aaron Tomlin , Ben Zhang , "Christoph Lameter" , Gilad Ben-Yossef , "Steven Rostedt" , , "Jonathan Corbet" , , Thomas Gleixner , Peter Zijlstra CC: Chris Metcalf Subject: [PATCH v10 1/3] smpboot: allow excluding cpus from the smpboot threads Date: Thu, 30 Apr 2015 15:39:24 -0400 Message-ID: <1430422766-19703-2-git-send-email-cmetcalf@ezchip.com> X-Mailer: git-send-email 2.1.2 In-Reply-To: <1430422766-19703-1-git-send-email-cmetcalf@ezchip.com> References: <1430422766-19703-1-git-send-email-cmetcalf@ezchip.com> X-EOPAttributedMessage: 0 X-Forefront-Antispam-Report: CIP:12.216.194.146;CTRY:US;IPV:NLI;EFV:NLI;SFV:NSPM;SFS:(10009020)(6009001)(339900001)(199003)(189002)(33646002)(5001770100001)(46102003)(50986999)(76176999)(6806004)(19580405001)(86362001)(104016003)(19580395003)(50466002)(48376002)(62966003)(77156002)(105606002)(85426001)(50226001)(2950100001)(87936001)(47776003)(106466001)(36756003)(229853001)(92566002)(42186005)(107886002)(5001960100002)(921003)(4001430100001)(1121003);DIR:OUT;SFP:1101;SCL:1;SRVR:AM2PR02MB0771;H:ld-1.internal.tilera.com;FPR:;SPF:Fail;MLV:sfv;A:1;MX:1;LANG:en; MIME-Version: 1.0 Content-Type: text/plain X-Microsoft-Antispam: UriScan:;BCL:0;PCL:0;RULEID:;SRVR:AM2PR02MB0771; X-Microsoft-Antispam-PRVS: X-Exchange-Antispam-Report-Test: UriScan:; X-Exchange-Antispam-Report-CFA-Test: BCL:0;PCL:0;RULEID:(601004)(5005006)(3002001);SRVR:AM2PR02MB0771;BCL:0;PCL:0;RULEID:;SRVR:AM2PR02MB0771; X-Forefront-PRVS: 056297E276 X-OriginatorOrg: ezchip.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 30 Apr 2015 19:39:31.6248 (UTC) X-MS-Exchange-CrossTenant-Id: 0fc16e0a-3cd3-4092-8b2f-0a42cff122c3 X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=0fc16e0a-3cd3-4092-8b2f-0a42cff122c3;Ip=[12.216.194.146];Helo=[ld-1.internal.tilera.com] X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: AM2PR02MB0771 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This change allows some cores to be excluded from running the smp_hotplug_thread tasks. The following commit to update kernel/watchdog.c to use this functionality is the motivating example, and more information on the motivation is provided there. A new smp_hotplug_thread field is introduced, "cpumask", which is cpumask field managed by the smpboot subsystem that indicates whether or not the given smp_hotplug_thread should run on that core; the cpumask is checked when deciding whether to unpark the thread. To limit the cpumask to less than cpu_possible, you must call smpboot_update_cpumask_percpu_thread() after registering. Signed-off-by: Chris Metcalf --- include/linux/smpboot.h | 5 +++++ kernel/smpboot.c | 55 ++++++++++++++++++++++++++++++++++++++++++++++++- 2 files changed, 59 insertions(+), 1 deletion(-) diff --git a/include/linux/smpboot.h b/include/linux/smpboot.h index d600afb21926..7c42153edfac 100644 --- a/include/linux/smpboot.h +++ b/include/linux/smpboot.h @@ -27,6 +27,8 @@ struct smpboot_thread_data; * @pre_unpark: Optional unpark function, called before the thread is * unparked (cpu online). This is not guaranteed to be * called on the target cpu of the thread. Careful! + * @cpumask: Internal state. To update which threads are unparked, + * call smpboot_update_cpumask_percpu_thread(). * @selfparking: Thread is not parked by the park function. * @thread_comm: The base name of the thread */ @@ -41,11 +43,14 @@ struct smp_hotplug_thread { void (*park)(unsigned int cpu); void (*unpark)(unsigned int cpu); void (*pre_unpark)(unsigned int cpu); + struct cpumask cpumask; bool selfparking; const char *thread_comm; }; int smpboot_register_percpu_thread(struct smp_hotplug_thread *plug_thread); void smpboot_unregister_percpu_thread(struct smp_hotplug_thread *plug_thread); +int smpboot_update_cpumask_percpu_thread(struct smp_hotplug_thread *plug_thread, + const struct cpumask *); #endif diff --git a/kernel/smpboot.c b/kernel/smpboot.c index c697f73d82d6..209750ab7031 100644 --- a/kernel/smpboot.c +++ b/kernel/smpboot.c @@ -232,7 +232,8 @@ void smpboot_unpark_threads(unsigned int cpu) mutex_lock(&smpboot_threads_lock); list_for_each_entry(cur, &hotplug_threads, list) - smpboot_unpark_thread(cur, cpu); + if (cpumask_test_cpu(cpu, &cur->cpumask)) + smpboot_unpark_thread(cur, cpu); mutex_unlock(&smpboot_threads_lock); } @@ -258,6 +259,15 @@ static void smpboot_destroy_threads(struct smp_hotplug_thread *ht) { unsigned int cpu; + /* Unpark any threads that were voluntarily parked. */ + for_each_cpu_not(cpu, &ht->cpumask) { + if (cpu_online(cpu)) { + struct task_struct *tsk = *per_cpu_ptr(ht->store, cpu); + if (tsk) + kthread_unpark(tsk); + } + } + /* We need to destroy also the parked threads of offline cpus */ for_each_possible_cpu(cpu) { struct task_struct *tsk = *per_cpu_ptr(ht->store, cpu); @@ -281,6 +291,7 @@ int smpboot_register_percpu_thread(struct smp_hotplug_thread *plug_thread) unsigned int cpu; int ret = 0; + cpumask_copy(&plug_thread->cpumask, cpu_possible_mask); get_online_cpus(); mutex_lock(&smpboot_threads_lock); for_each_online_cpu(cpu) { @@ -316,6 +327,48 @@ void smpboot_unregister_percpu_thread(struct smp_hotplug_thread *plug_thread) } EXPORT_SYMBOL_GPL(smpboot_unregister_percpu_thread); +/** + * smpboot_update_cpumask_percpu_thread - Adjust which per_cpu hotplug threads stay parked + * @plug_thread: Hotplug thread descriptor + * @new: Revised mask to use + * + * The cpumask field in the smp_hotplug_thread must not be updated directly + * by the client, but only by calling this function. + */ +int smpboot_update_cpumask_percpu_thread(struct smp_hotplug_thread *plug_thread, + const struct cpumask *new) +{ + struct cpumask *old = &plug_thread->cpumask; + cpumask_var_t tmp; + unsigned int cpu; + + if (!alloc_cpumask_var(&tmp, GFP_KERNEL)) + return -ENOMEM; + + get_online_cpus(); + mutex_lock(&smpboot_threads_lock); + + /* Park threads that were exclusively enabled on the old mask. */ + cpumask_andnot(tmp, old, new); + for_each_cpu_and(cpu, tmp, cpu_online_mask) + smpboot_park_thread(plug_thread, cpu); + + /* Unpark threads that are exclusively enabled on the new mask. */ + cpumask_andnot(tmp, new, old); + for_each_cpu_and(cpu, tmp, cpu_online_mask) + smpboot_unpark_thread(plug_thread, cpu); + + cpumask_copy(old, new); + + mutex_unlock(&smpboot_threads_lock); + put_online_cpus(); + + free_cpumask_var(tmp); + + return 0; +} +EXPORT_SYMBOL_GPL(smpboot_update_cpumask_percpu_thread); + static DEFINE_PER_CPU(atomic_t, cpu_hotplug_state) = ATOMIC_INIT(CPU_POST_DEAD); /* -- 2.1.2