From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ob0-f179.google.com (mail-ob0-f179.google.com [209.85.214.179]) (using TLSv1 with cipher ECDHE-RSA-RC4-SHA (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority" (not verified)) by ozlabs.org (Postfix) with ESMTPS id D58FAB6F13 for ; Mon, 23 Apr 2012 17:09:54 +1000 (EST) Received: by mail-ob0-f179.google.com with SMTP id uo19so7505922obb.38 for ; Mon, 23 Apr 2012 00:09:54 -0700 (PDT) Date: Mon, 23 Apr 2012 00:08:38 -0700 From: Anton Vorontsov To: Andrew Morton , Oleg Nesterov 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 In-Reply-To: <20120423070641.GA27702@lizard> Cc: linaro-kernel@lists.linaro.org, Mike Frysinger , Peter Zijlstra , user-mode-linux-devel@lists.sourceforge.net, linux-sh@vger.kernel.org, Richard Weinberger , patches@linaro.org, linux-kernel@vger.kernel.org, uclinux-dist-devel@blackfin.uclinux.org, linux-mm@kvack.org, Paul Mundt , John Stultz , KOSAKI Motohiro , Russell King , linuxppc-dev@lists.ozlabs.org, linux-arm-kernel@lists.infradead.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , 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