Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753516Ab3IHPWk (ORCPT ); Sun, 8 Sep 2013 11:22:40 -0400 Received: from mail-pa0-f48.google.com ([209.85.220.48]:37167 "EHLO mail-pa0-f48.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752748Ab3IHPWi (ORCPT ); Sun, 8 Sep 2013 11:22:38 -0400 From: Jiang Liu To: Andrew Morton , Shaohua Li , Wang YanQing Cc: liuj97@gmail.com, Jiang Liu , Peter Zijlstra , Ingo Molnar , Steven Rostedt , Paul Gortmaker , liguang , linux-kernel@vger.kernel.org Subject: [PATCH v1 1/3] SMP: kill redundant call_function_data->cpumask_ipi field Date: Sun, 8 Sep 2013 23:22:23 +0800 Message-Id: <1378653745-8343-1-git-send-email-liuj97@gmail.com> X-Mailer: git-send-email 1.8.1.2 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4116 Lines: 117 From: Jiang Liu Commit f44310b98ddb7 "smp: Fix SMP function call empty cpu mask race" introduced field call_function_data->cpumask_ipi to resolve a race condition in smp_call_function_many(). Later commit 9a46ad6d6df3 "smp: make smp_call_function_many() use logic similar to smp_call_function_single()" fixed the same issue in another way when optimizing smp_call_function_many(), which then obsoletes changes introduced by commit f44310b98ddb7. So revert it. We may also keep call_function_data->cpumask_ipi field and use it to optimize smp_call_function_many() as below: diff --git a/kernel/smp.c b/kernel/smp.c index fe9f773..dd852fb 100644 --- a/kernel/smp.c +++ b/kernel/smp.c @@ -428,6 +428,8 @@ void smp_call_function_many(const struct cpumask *mask, csd->info = info; raw_spin_lock_irqsave(&dst->lock, flags); + if (list_empty(&dst->list)) + cpumask_clear_cpu(cpu, cfd->cpumask_ipi); list_add_tail(&csd->list, &dst->list); raw_spin_unlock_irqrestore(&dst->lock, flags); } But I have no platforms to verify the optimization effect, so simpify the code first. Signed-off-by: Jiang Liu Cc: Jiang Liu Cc: Andrew Morton Cc: Wang YanQing Cc: Shaohua Li Cc: Peter Zijlstra Cc: Ingo Molnar Cc: Steven Rostedt Cc: Paul Gortmaker Cc: liguang Cc: linux-kernel@vger.kernel.org --- kernel/smp.c | 16 ++-------------- 1 file changed, 2 insertions(+), 14 deletions(-) diff --git a/kernel/smp.c b/kernel/smp.c index fe9f773..a034712 100644 --- a/kernel/smp.c +++ b/kernel/smp.c @@ -23,7 +23,6 @@ enum { struct call_function_data { struct call_single_data __percpu *csd; cpumask_var_t cpumask; - cpumask_var_t cpumask_ipi; }; static DEFINE_PER_CPU_SHARED_ALIGNED(struct call_function_data, cfd_data); @@ -47,9 +46,6 @@ hotplug_cfd(struct notifier_block *nfb, unsigned long action, void *hcpu) if (!zalloc_cpumask_var_node(&cfd->cpumask, GFP_KERNEL, cpu_to_node(cpu))) return notifier_from_errno(-ENOMEM); - if (!zalloc_cpumask_var_node(&cfd->cpumask_ipi, GFP_KERNEL, - cpu_to_node(cpu))) - return notifier_from_errno(-ENOMEM); cfd->csd = alloc_percpu(struct call_single_data); if (!cfd->csd) { free_cpumask_var(cfd->cpumask); @@ -64,7 +60,6 @@ hotplug_cfd(struct notifier_block *nfb, unsigned long action, void *hcpu) case CPU_DEAD: case CPU_DEAD_FROZEN: free_cpumask_var(cfd->cpumask); - free_cpumask_var(cfd->cpumask_ipi); free_percpu(cfd->csd); break; #endif @@ -255,9 +250,9 @@ int smp_call_function_single(int cpu, smp_call_func_t func, void *info, csd = &__get_cpu_var(csd_data); csd_lock(csd); - csd->func = func; csd->info = info; + generic_exec_single(cpu, csd, wait); } else { err = -ENXIO; /* CPU not online */ @@ -410,13 +405,6 @@ void smp_call_function_many(const struct cpumask *mask, if (unlikely(!cpumask_weight(cfd->cpumask))) return; - /* - * After we put an entry into the list, cfd->cpumask may be cleared - * again when another CPU sends another IPI for a SMP function call, so - * cfd->cpumask will be zero. - */ - cpumask_copy(cfd->cpumask_ipi, cfd->cpumask); - for_each_cpu(cpu, cfd->cpumask) { struct call_single_data *csd = per_cpu_ptr(cfd->csd, cpu); struct call_single_queue *dst = @@ -433,7 +421,7 @@ void smp_call_function_many(const struct cpumask *mask, } /* Send a message to all CPUs in the map */ - arch_send_call_function_ipi_mask(cfd->cpumask_ipi); + arch_send_call_function_ipi_mask(cfd->cpumask); if (wait) { for_each_cpu(cpu, cfd->cpumask) { -- 1.8.1.2 -- 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/