From patchwork Thu Jun 27 19:54:39 2013 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Srivatsa S. 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Bhat" Subject: [PATCH v3 13/45] sched/fair: 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, 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, Ingo Molnar , Peter Zijlstra , "Srivatsa S. Bhat" Date: Fri, 28 Jun 2013 01:24:39 +0530 Message-ID: <20130627195439.29830.96122.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 X-TM-AS-MML: No X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13062719-4790-0000-0000-00000902DE9F Sender: linux-pm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org X-Spam-Status: No, score=-8.2 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP 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: Ingo Molnar Cc: Peter Zijlstra Signed-off-by: Srivatsa S. Bhat --- kernel/sched/fair.c | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) -- To unsubscribe from this list: send the line "unsubscribe linux-pm" 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/kernel/sched/fair.c b/kernel/sched/fair.c index f77f9c5..62d98dd 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -3369,7 +3369,8 @@ done: * * Returns the target CPU number, or the same CPU if no balancing is needed. * - * preempt must be disabled. + * Must be called within get/put_online_cpus_atomic(), to prevent CPUs + * from going offline from under us. */ static int select_task_rq_fair(struct task_struct *p, int sd_flag, int wake_flags) @@ -5289,6 +5290,8 @@ void idle_balance(int this_cpu, struct rq *this_rq) raw_spin_unlock(&this_rq->lock); update_blocked_averages(this_cpu); + + get_online_cpus_atomic(); rcu_read_lock(); for_each_domain(this_cpu, sd) { unsigned long interval; @@ -5312,6 +5315,7 @@ void idle_balance(int this_cpu, struct rq *this_rq) } } rcu_read_unlock(); + put_online_cpus_atomic(); raw_spin_lock(&this_rq->lock); @@ -5338,6 +5342,7 @@ static int active_load_balance_cpu_stop(void *data) struct rq *target_rq = cpu_rq(target_cpu); struct sched_domain *sd; + get_online_cpus_atomic(); raw_spin_lock_irq(&busiest_rq->lock); /* make sure the requested cpu hasn't gone down in the meantime */ @@ -5389,6 +5394,7 @@ static int active_load_balance_cpu_stop(void *data) out_unlock: busiest_rq->active_balance = 0; raw_spin_unlock_irq(&busiest_rq->lock); + put_online_cpus_atomic(); return 0; } @@ -5549,6 +5555,7 @@ static void rebalance_domains(int cpu, enum cpu_idle_type idle) update_blocked_averages(cpu); + get_online_cpus_atomic(); rcu_read_lock(); for_each_domain(cpu, sd) { if (!(sd->flags & SD_LOAD_BALANCE)) @@ -5597,6 +5604,7 @@ out: break; } rcu_read_unlock(); + put_online_cpus_atomic(); /* * next_balance will be updated only when there is a need. @@ -5728,6 +5736,7 @@ static void run_rebalance_domains(struct softirq_action *h) enum cpu_idle_type idle = this_rq->idle_balance ? CPU_IDLE : CPU_NOT_IDLE; + get_online_cpus_atomic(); rebalance_domains(this_cpu, idle); /* @@ -5736,6 +5745,7 @@ static void run_rebalance_domains(struct softirq_action *h) * stopped. */ nohz_idle_balance(this_cpu, idle); + put_online_cpus_atomic(); } static inline int on_null_domain(int cpu) @@ -5753,8 +5763,10 @@ void trigger_load_balance(struct rq *rq, int cpu) likely(!on_null_domain(cpu))) raise_softirq(SCHED_SOFTIRQ); #ifdef CONFIG_NO_HZ_COMMON + get_online_cpus_atomic(); if (nohz_kick_needed(rq, cpu) && likely(!on_null_domain(cpu))) nohz_balancer_kick(cpu); + put_online_cpus_atomic(); #endif }