Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752111Ab3FWNnk (ORCPT ); Sun, 23 Jun 2013 09:43:40 -0400 Received: from e28smtp05.in.ibm.com ([122.248.162.5]:47808 "EHLO e28smtp05.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751763Ab3FWNnf (ORCPT ); Sun, 23 Jun 2013 09:43:35 -0400 From: "Srivatsa S. Bhat" Subject: [PATCH 09/45] smp: 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 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, Andrew Morton , Wang YanQing , Shaohua Li , Jan Beulich , liguang Date: Sun, 23 Jun 2013 19:10:13 +0530 Message-ID: <20130623134008.19094.98716.stgit@srivatsabhat.in.ibm.com> In-Reply-To: <20130623133642.19094.16038.stgit@srivatsabhat.in.ibm.com> References: <20130623133642.19094.16038.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: 13062313-8256-0000-0000-0000080B6404 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 6626 Lines: 220 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: Andrew Morton Cc: Wang YanQing Cc: Shaohua Li Cc: Jan Beulich Cc: liguang Signed-off-by: Srivatsa S. Bhat --- kernel/smp.c | 52 ++++++++++++++++++++++++++++++---------------------- 1 file changed, 30 insertions(+), 22 deletions(-) diff --git a/kernel/smp.c b/kernel/smp.c index 4dba0f7..1f36d6d 100644 --- a/kernel/smp.c +++ b/kernel/smp.c @@ -232,7 +232,7 @@ int smp_call_function_single(int cpu, smp_call_func_t func, void *info, * prevent preemption and reschedule on another processor, * as well as CPU removal */ - this_cpu = get_cpu(); + this_cpu = get_online_cpus_atomic(); /* * Can deadlock when called with interrupts disabled. @@ -264,7 +264,7 @@ int smp_call_function_single(int cpu, smp_call_func_t func, void *info, } } - put_cpu(); + put_online_cpus_atomic(); return err; } @@ -294,7 +294,7 @@ int smp_call_function_any(const struct cpumask *mask, int ret; /* Try for same CPU (cheapest) */ - cpu = get_cpu(); + cpu = get_online_cpus_atomic(); if (cpumask_test_cpu(cpu, mask)) goto call; @@ -310,7 +310,7 @@ int smp_call_function_any(const struct cpumask *mask, cpu = cpumask_any_and(mask, cpu_online_mask); call: ret = smp_call_function_single(cpu, func, info, wait); - put_cpu(); + put_online_cpus_atomic(); return ret; } EXPORT_SYMBOL_GPL(smp_call_function_any); @@ -331,7 +331,8 @@ void __smp_call_function_single(int cpu, struct call_single_data *csd, unsigned int this_cpu; unsigned long flags; - this_cpu = get_cpu(); + this_cpu = get_online_cpus_atomic(); + /* * Can deadlock when called with interrupts disabled. * We allow cpu's that are not yet online though, as no one else can @@ -349,7 +350,8 @@ void __smp_call_function_single(int cpu, struct call_single_data *csd, csd_lock(csd); generic_exec_single(cpu, csd, wait); } - put_cpu(); + + put_online_cpus_atomic(); } /** @@ -370,7 +372,9 @@ void smp_call_function_many(const struct cpumask *mask, smp_call_func_t func, void *info, bool wait) { struct call_function_data *cfd; - int cpu, next_cpu, this_cpu = smp_processor_id(); + int cpu, next_cpu, this_cpu; + + this_cpu = get_online_cpus_atomic(); /* * Can deadlock when called with interrupts disabled. @@ -388,7 +392,7 @@ void smp_call_function_many(const struct cpumask *mask, /* No online cpus? We're done. */ if (cpu >= nr_cpu_ids) - return; + goto out; /* Do we have another CPU which isn't us? */ next_cpu = cpumask_next_and(cpu, mask, cpu_online_mask); @@ -398,7 +402,7 @@ void smp_call_function_many(const struct cpumask *mask, /* Fastpath: do that cpu by itself. */ if (next_cpu >= nr_cpu_ids) { smp_call_function_single(cpu, func, info, wait); - return; + goto out; } cfd = &__get_cpu_var(cfd_data); @@ -408,7 +412,7 @@ void smp_call_function_many(const struct cpumask *mask, /* Some callers race with other cpus changing the passed mask */ if (unlikely(!cpumask_weight(cfd->cpumask))) - return; + goto out; /* * After we put an entry into the list, cfd->cpumask may be cleared @@ -443,6 +447,9 @@ void smp_call_function_many(const struct cpumask *mask, csd_lock_wait(csd); } } + +out: + put_online_cpus_atomic(); } EXPORT_SYMBOL(smp_call_function_many); @@ -463,9 +470,9 @@ EXPORT_SYMBOL(smp_call_function_many); */ int smp_call_function(smp_call_func_t func, void *info, int wait) { - preempt_disable(); + get_online_cpus_atomic(); smp_call_function_many(cpu_online_mask, func, info, wait); - preempt_enable(); + put_online_cpus_atomic(); return 0; } @@ -565,12 +572,12 @@ int on_each_cpu(void (*func) (void *info), void *info, int wait) unsigned long flags; int ret = 0; - preempt_disable(); + get_online_cpus_atomic(); ret = smp_call_function(func, info, wait); local_irq_save(flags); func(info); local_irq_restore(flags); - preempt_enable(); + put_online_cpus_atomic(); return ret; } EXPORT_SYMBOL(on_each_cpu); @@ -592,7 +599,7 @@ EXPORT_SYMBOL(on_each_cpu); void on_each_cpu_mask(const struct cpumask *mask, smp_call_func_t func, void *info, bool wait) { - int cpu = get_cpu(); + unsigned int cpu = get_online_cpus_atomic(); smp_call_function_many(mask, func, info, wait); if (cpumask_test_cpu(cpu, mask)) { @@ -600,7 +607,7 @@ void on_each_cpu_mask(const struct cpumask *mask, smp_call_func_t func, func(info); local_irq_enable(); } - put_cpu(); + put_online_cpus_atomic(); } EXPORT_SYMBOL(on_each_cpu_mask); @@ -625,8 +632,9 @@ EXPORT_SYMBOL(on_each_cpu_mask); * The function might sleep if the GFP flags indicates a non * atomic allocation is allowed. * - * Preemption is disabled to protect against CPUs going offline but not online. - * CPUs going online during the call will not be seen or sent an IPI. + * We use get/put_online_cpus_atomic() to protect against CPUs going + * offline but not online. CPUs going online during the call will + * not be seen or sent an IPI. * * You must not call this function with disabled interrupts or * from a hardware interrupt handler or from a bottom half handler. @@ -641,26 +649,26 @@ void on_each_cpu_cond(bool (*cond_func)(int cpu, void *info), might_sleep_if(gfp_flags & __GFP_WAIT); if (likely(zalloc_cpumask_var(&cpus, (gfp_flags|__GFP_NOWARN)))) { - preempt_disable(); + get_online_cpus_atomic(); for_each_online_cpu(cpu) if (cond_func(cpu, info)) cpumask_set_cpu(cpu, cpus); on_each_cpu_mask(cpus, func, info, wait); - preempt_enable(); + put_online_cpus_atomic(); free_cpumask_var(cpus); } else { /* * No free cpumask, bother. No matter, we'll * just have to IPI them one by one. */ - preempt_disable(); + get_online_cpus_atomic(); for_each_online_cpu(cpu) if (cond_func(cpu, info)) { ret = smp_call_function_single(cpu, func, info, wait); WARN_ON_ONCE(!ret); } - preempt_enable(); + put_online_cpus_atomic(); } } EXPORT_SYMBOL(on_each_cpu_cond); -- 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/