From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from e28smtp02.in.ibm.com (e28smtp02.in.ibm.com [122.248.162.2]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client CN "e28smtp02.in.ibm.com", Issuer "GeoTrust SSL CA" (not verified)) by ozlabs.org (Postfix) with ESMTPS id 79ABC2C03C6 for ; Wed, 26 Jun 2013 06:29:57 +1000 (EST) Received: from /spool/local by e28smtp02.in.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Wed, 26 Jun 2013 01:51:58 +0530 Received: from d28relay02.in.ibm.com (d28relay02.in.ibm.com [9.184.220.59]) by d28dlp02.in.ibm.com (Postfix) with ESMTP id 4A28F394004F for ; Wed, 26 Jun 2013 01:59:51 +0530 (IST) Received: from d28av03.in.ibm.com (d28av03.in.ibm.com [9.184.220.65]) by d28relay02.in.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id r5PKU9Kv16056350 for ; Wed, 26 Jun 2013 02:00:10 +0530 Received: from d28av03.in.ibm.com (loopback [127.0.0.1]) by d28av03.in.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id r5PKTng5012093 for ; Wed, 26 Jun 2013 06:29:51 +1000 From: "Srivatsa S. Bhat" Subject: [PATCH v2 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 Date: Wed, 26 Jun 2013 01:56:34 +0530 Message-ID: <20130625202634.16593.17645.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> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Cc: linux-arch@vger.kernel.org, nikunj@linux.vnet.ibm.com, zhong@linux.vnet.ibm.com, linux-pm@vger.kernel.org, fweisbec@gmail.com, "Rafael J. Wysocki" , linux-kernel@vger.kernel.org, rostedt@goodmis.org, xiaoguangrong@linux.vnet.ibm.com, sbw@mit.edu, Yasuaki Ishimatsu , wangyun@linux.vnet.ibm.com, "Srivatsa S. Bhat" , netdev@vger.kernel.org, Thomas Gleixner , linuxppc-dev@lists.ozlabs.org, Andrew Morton List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , 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)