From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754026Ab2LESqD (ORCPT ); Wed, 5 Dec 2012 13:46:03 -0500 Received: from e23smtp08.au.ibm.com ([202.81.31.141]:49633 "EHLO e23smtp08.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753949Ab2LESp7 (ORCPT ); Wed, 5 Dec 2012 13:45:59 -0500 From: "Srivatsa S. Bhat" Subject: [RFC PATCH v2 08/10] yield_to(), cpu-hotplug: Prevent offlining of other CPUs properly 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 Date: Thu, 06 Dec 2012 00:14:28 +0530 Message-ID: <20121205184426.3750.33584.stgit@srivatsabhat.in.ibm.com> In-Reply-To: <20121205184041.3750.64945.stgit@srivatsabhat.in.ibm.com> References: <20121205184041.3750.64945.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-Content-Scanned: Fidelis XPS MAILER x-cbid: 12120518-5140-0000-0000-0000027833C7 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Once stop_machine() is gone from the CPU offline path, we won't be able to depend on local_irq_save() to prevent CPUs from going offline from under us. Use the get/put_online_cpus_atomic_light() APIs to prevent changes to the cpu_online_mask, while invoking from atomic context. Signed-off-by: Srivatsa S. Bhat --- kernel/sched/core.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 84a8579..1ef595a 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -4312,6 +4312,7 @@ bool __sched yield_to(struct task_struct *p, bool preempt) unsigned long flags; bool yielded = 0; + get_online_cpus_atomic_light(); local_irq_save(flags); rq = this_rq(); @@ -4339,13 +4340,14 @@ again: * Make p's CPU reschedule; pick_next_entity takes care of * fairness. */ - if (preempt && rq != p_rq) + if (preempt && rq != p_rq && cpu_online(task_cpu(p))) resched_task(p_rq->curr); } out: double_rq_unlock(rq, p_rq); local_irq_restore(flags); + put_online_cpus_atomic_light(); if (yielded) schedule();