From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Srivatsa S. Bhat" Subject: [RFC PATCH v4 6/9] kick_process(), cpu-hotplug: Prevent offlining of target CPU properly Date: Tue, 11 Dec 2012 19:35:11 +0530 Message-ID: <20121211140510.23621.90911.stgit@srivatsabhat.in.ibm.com> References: <20121211140314.23621.64088.stgit@srivatsabhat.in.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Return-path: Received: from e28smtp04.in.ibm.com ([122.248.162.4]:47654 "EHLO e28smtp04.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753529Ab2LKOGn (ORCPT ); Tue, 11 Dec 2012 09:06:43 -0500 Received: from /spool/local by e28smtp04.in.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 11 Dec 2012 19:36:21 +0530 In-Reply-To: <20121211140314.23621.64088.stgit@srivatsabhat.in.ibm.com> Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: tglx@linutronix.de, peterz@infradead.org, paulmck@linux.vnet.ibm.com, rusty@rustcorp.com.au, mingo@kernel.org, akpm@linux-foundation.org, namhyung@kernel.org, vincent.guittot@linaro.org, tj@kernel.org, oleg@redhat.com Cc: sbw@mit.edu, amit.kucheria@linaro.org, rostedt@goodmis.org, rjw@sisk.pl, srivatsa.bhat@linux.vnet.ibm.com, wangyun@linux.vnet.ibm.com, xiaoguangrong@linux.vnet.ibm.com, nikunj@linux.vnet.ibm.com, linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org Once stop_machine() is gone from the CPU offline path, we won't be able to depend on preempt_disable() 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. Signed-off-by: Srivatsa S. Bhat --- kernel/sched/core.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index f51e0aa..cff7656 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -1091,11 +1091,11 @@ void kick_process(struct task_struct *p) { int cpu; - preempt_disable(); + get_online_cpus_atomic(); cpu = task_cpu(p); if ((cpu != smp_processor_id()) && task_curr(p)) smp_send_reschedule(cpu); - preempt_enable(); + put_online_cpus_atomic(); } EXPORT_SYMBOL_GPL(kick_process); #endif /* CONFIG_SMP */