Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754362Ab3F0T4w (ORCPT ); Thu, 27 Jun 2013 15:56:52 -0400 Received: from e28smtp05.in.ibm.com ([122.248.162.5]:33088 "EHLO e28smtp05.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754333Ab3F0T4r (ORCPT ); Thu, 27 Jun 2013 15:56:47 -0400 From: "Srivatsa S. Bhat" Subject: [PATCH v3 05/45] CPU hotplug: Protect set_cpu_online() to avoid false-positives 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, David.Laight@aculab.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, Thomas Gleixner , Andrew Morton , Yasuaki Ishimatsu , "Rafael J. Wysocki" , "Srivatsa S. Bhat" Date: Fri, 28 Jun 2013 01:23:24 +0530 Message-ID: <20130627195324.29830.11378.stgit@srivatsabhat.in.ibm.com> In-Reply-To: <20130627195136.29830.10445.stgit@srivatsabhat.in.ibm.com> References: <20130627195136.29830.10445.stgit@srivatsabhat.in.ibm.com> User-Agent: StGIT/0.14.3 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-TM-AS-MML: No X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13062719-8256-0000-0000-0000081CBBFB Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1643 Lines: 48 When bringing a secondary CPU online, the task running on the CPU coming up sets itself in the cpu_online_mask. This is safe even though this task is not the hotplug writer task. But it is kinda hard to teach this to the CPU hotplug debug infrastructure, and if we get it wrong, we risk making the debug code too lenient, risking false-negatives. Luckily, all architectures use set_cpu_online() to manipulate the cpu_online_mask. So, to avoid false-positive warnings from the CPU hotplug debug code, encapsulate the body of set_cpu_online() within get/put_online_cpus_atomic(). Cc: Thomas Gleixner Cc: Andrew Morton Cc: Yasuaki Ishimatsu Cc: "Rafael J. Wysocki" Signed-off-by: Srivatsa S. Bhat --- kernel/cpu.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/kernel/cpu.c b/kernel/cpu.c index 5297ec1..35e7115 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -832,10 +832,14 @@ void set_cpu_present(unsigned int cpu, bool present) void set_cpu_online(unsigned int cpu, bool online) { + get_online_cpus_atomic(); + if (online) cpumask_set_cpu(cpu, to_cpumask(cpu_online_bits)); else cpumask_clear_cpu(cpu, to_cpumask(cpu_online_bits)); + + put_online_cpus_atomic(); } void set_cpu_active(unsigned int cpu, bool active) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/