From patchwork Tue Jun 25 20:29:43 2013 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Srivatsa S. Bhat" X-Patchwork-Id: 254369 X-Patchwork-Delegate: davem@davemloft.net Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id B285A2C1365 for ; Wed, 26 Jun 2013 06:42:35 +1000 (EST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753507Ab3FYUdO (ORCPT ); Tue, 25 Jun 2013 16:33:14 -0400 Received: from e28smtp04.in.ibm.com ([122.248.162.4]:59544 "EHLO e28smtp04.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753402Ab3FYUdJ (ORCPT ); Tue, 25 Jun 2013 16:33:09 -0400 Received: from /spool/local by e28smtp04.in.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Wed, 26 Jun 2013 01:56:52 +0530 Received: from d28dlp01.in.ibm.com (9.184.220.126) by e28smtp04.in.ibm.com (192.168.1.134) with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted; Wed, 26 Jun 2013 01:56:50 +0530 Received: from d28relay01.in.ibm.com (d28relay01.in.ibm.com [9.184.220.58]) by d28dlp01.in.ibm.com (Postfix) with ESMTP id E2BDBE0054; Wed, 26 Jun 2013 02:02:36 +0530 (IST) Received: from d28av01.in.ibm.com (d28av01.in.ibm.com [9.184.220.63]) by d28relay01.in.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id r5PKXJoI21364850; Wed, 26 Jun 2013 02:03:19 +0530 Received: from d28av01.in.ibm.com (loopback [127.0.0.1]) by d28av01.in.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id r5PKWvpT003517; Tue, 25 Jun 2013 20:33:02 GMT Received: from srivatsabhat.in.ibm.com ([9.79.199.80]) by d28av01.in.ibm.com (8.14.4/8.13.1/NCO v10.0 AVin) with ESMTP id r5PKWum6003486; Tue, 25 Jun 2013 20:32:56 GMT From: "Srivatsa S. Bhat" Subject: [PATCH v2 22/45] percpu_counter: Use get/put_online_cpus_atomic() to prevent CPU offline To: tglx@linutronix.de, peterz@infradead.org, tj@kernel.org, oleg@redhat.com, paulmck@linux.vnet.ibm.com, rusty@rustcorp.com.au, mingo@kernel.org, akpm@linux-foundation.org, namhyung@kernel.org, walken@google.com, vincent.guittot@linaro.org, laijs@cn.fujitsu.com Cc: rostedt@goodmis.org, wangyun@linux.vnet.ibm.com, xiaoguangrong@linux.vnet.ibm.com, sbw@mit.edu, fweisbec@gmail.com, zhong@linux.vnet.ibm.com, nikunj@linux.vnet.ibm.com, srivatsa.bhat@linux.vnet.ibm.com, linux-pm@vger.kernel.org, linux-arch@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Al Viro , Tejun Heo , "Srivatsa S. Bhat" Date: Wed, 26 Jun 2013 01:59:43 +0530 Message-ID: <20130625202943.16593.52711.stgit@srivatsabhat.in.ibm.com> In-Reply-To: <20130625202452.16593.22810.stgit@srivatsabhat.in.ibm.com> References: <20130625202452.16593.22810.stgit@srivatsabhat.in.ibm.com> User-Agent: StGIT/0.14.3 MIME-Version: 1.0 X-TM-AS-MML: No X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13062520-5564-0000-0000-0000088562A3 Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org Once stop_machine() is gone from the CPU offline path, we won't be able to depend on disabling preemption to prevent CPUs from going offline from under us. Use the get/put_online_cpus_atomic() APIs to prevent CPUs from going offline, while invoking from atomic context. Cc: Al Viro Cc: Tejun Heo Signed-off-by: Srivatsa S. Bhat --- lib/percpu_counter.c | 10 ++++++++++ 1 file changed, 10 insertions(+) -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html diff --git a/lib/percpu_counter.c b/lib/percpu_counter.c index ba6085d..f5e718d 100644 --- a/lib/percpu_counter.c +++ b/lib/percpu_counter.c @@ -98,6 +98,15 @@ s64 __percpu_counter_sum(struct percpu_counter *fbc) s64 ret; int cpu; + /* + * The calls to get/put_online_cpus_atomic() is strictly not + * necessary, since CPU hotplug is explicitly handled via the + * hotplug callback which synchronizes through fbc->lock. + * But we add them here anyway to make it easier for the debug + * code under CONFIG_DEBUG_HOTPLUG_CPU to validate the correctness + * of hotplug synchronization. + */ + get_online_cpus_atomic(); raw_spin_lock(&fbc->lock); ret = fbc->count; for_each_online_cpu(cpu) { @@ -105,6 +114,7 @@ s64 __percpu_counter_sum(struct percpu_counter *fbc) ret += *pcount; } raw_spin_unlock(&fbc->lock); + put_online_cpus_atomic(); return ret; } EXPORT_SYMBOL(__percpu_counter_sum);