From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754046Ab2DWHJ5 (ORCPT ); Mon, 23 Apr 2012 03:09:57 -0400 Received: from mail-ob0-f174.google.com ([209.85.214.174]:45494 "EHLO mail-ob0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750945Ab2DWHJy (ORCPT ); Mon, 23 Apr 2012 03:09:54 -0400 Date: Mon, 23 Apr 2012 00:08:38 -0700 From: Anton Vorontsov To: Andrew Morton , Oleg Nesterov Cc: Russell King , Mike Frysinger , Benjamin Herrenschmidt , Richard Weinberger , Paul Mundt , Peter Zijlstra , KOSAKI Motohiro , John Stultz , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, uclinux-dist-devel@blackfin.uclinux.org, linuxppc-dev@lists.ozlabs.org, linux-sh@vger.kernel.org, user-mode-linux-devel@lists.sourceforge.net, linaro-kernel@lists.linaro.org, patches@linaro.org, linux-mm@kvack.org Subject: [PATCH 3/9] powerpc: Use clear_tasks_mm_cpumask() Message-ID: <20120423070838.GC30752@lizard> References: <20120423070641.GA27702@lizard> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20120423070641.GA27702@lizard> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Current CPU hotplug code has some task->mm handling issues: 1. Working with task->mm w/o getting mm or grabing the task lock is dangerous as ->mm might disappear (exit_mm() assigns NULL under task_lock(), so tasklist lock is not enough). We can't use get_task_mm()/mmput() pair as mmput() might sleep, so we must take the task lock while handle its mm. 2. Checking for process->mm is not enough because process' main thread may exit or detach its mm via use_mm(), but other threads may still have a valid mm. To fix this we would need to use find_lock_task_mm(), which would walk up all threads and returns an appropriate task (with task lock held). clear_tasks_mm_cpumask() has all the issues fixed, so let's use it. Suggested-by: Oleg Nesterov Signed-off-by: Anton Vorontsov --- arch/powerpc/mm/mmu_context_nohash.c | 11 ++--------- 1 file changed, 2 insertions(+), 9 deletions(-) diff --git a/arch/powerpc/mm/mmu_context_nohash.c b/arch/powerpc/mm/mmu_context_nohash.c index 5b63bd3..e779642 100644 --- a/arch/powerpc/mm/mmu_context_nohash.c +++ b/arch/powerpc/mm/mmu_context_nohash.c @@ -333,9 +333,7 @@ static int __cpuinit mmu_context_cpu_notify(struct notifier_block *self, unsigned long action, void *hcpu) { unsigned int cpu = (unsigned int)(long)hcpu; -#ifdef CONFIG_HOTPLUG_CPU - struct task_struct *p; -#endif + /* We don't touch CPU 0 map, it's allocated at aboot and kept * around forever */ @@ -358,12 +356,7 @@ static int __cpuinit mmu_context_cpu_notify(struct notifier_block *self, stale_map[cpu] = NULL; /* We also clear the cpu_vm_mask bits of CPUs going away */ - read_lock(&tasklist_lock); - for_each_process(p) { - if (p->mm) - cpumask_clear_cpu(cpu, mm_cpumask(p->mm)); - } - read_unlock(&tasklist_lock); + clear_tasks_mm_cpumask(cpu); break; #endif /* CONFIG_HOTPLUG_CPU */ } -- 1.7.9.2