Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752463AbYJWPKr (ORCPT ); Thu, 23 Oct 2008 11:10:47 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754074AbYJWPKW (ORCPT ); Thu, 23 Oct 2008 11:10:22 -0400 Received: from ozlabs.org ([203.10.76.45]:51718 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752858AbYJWPKU (ORCPT ); Thu, 23 Oct 2008 11:10:20 -0400 From: Rusty Russell To: Oleg Nesterov Subject: Re: [PATCH 1/7] work_on_cpu: helper for doing task on a CPU. Date: Fri, 24 Oct 2008 02:10:22 +1100 User-Agent: KMail/1.9.10 Cc: linux-kernel@vger.kernel.org, travis@sgi.com, Ingo Molnar , Gautham R Shenoy References: <20081023005751.53973DDEFE@ozlabs.org> <20081023094036.GA7593@redhat.com> In-Reply-To: <20081023094036.GA7593@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200810240210.23085.rusty@rustcorp.com.au> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2980 Lines: 108 On Thursday 23 October 2008 20:40:36 Oleg Nesterov wrote: > Once we drop cpu_hotplug lock, CPU can go away and this work can migrate > to another cpu. Thanks Oleg. It is wrong. I'll use your suggestion; it's simpler. Cheers, Rusty. work_on_cpu: helper for doing task on a CPU. Several places in the kernel do the following: saved_mask = current->cpus_allowed; set_cpus_allowed_ptr(current, &cpumask_of_cpu(pr->id)); somefunc(); /* restore the previous state */ set_cpus_allowed_ptr(current, &saved_mask); This is bad, because a process's cpumask is observable and manipulatable by userspace and should not be toyed with. We have the infrastructure, this just creates a nice wrapper to encourage its use. Signed-off-by: Rusty Russell Cc: Ingo Molnar --- include/linux/workqueue.h | 8 ++++++++ kernel/workqueue.c | 45 +++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 53 insertions(+) diff -r 494880dd124b include/linux/workqueue.h --- a/include/linux/workqueue.h Fri Oct 24 00:29:43 2008 +1100 +++ b/include/linux/workqueue.h Fri Oct 24 01:16:52 2008 +1100 @@ -240,4 +240,12 @@ void cancel_rearming_delayed_work(struct cancel_delayed_work_sync(work); } +#ifndef CONFIG_SMP +static inline long work_on_cpu(unsigned int cpu, long (*fn)(void *), void *arg) +{ + return fn(arg); +} +#else +long work_on_cpu(unsigned int cpu, long (*fn)(void *), void *arg); +#endif /* CONFIG_SMP */ #endif diff -r 494880dd124b kernel/workqueue.c --- a/kernel/workqueue.c Fri Oct 24 00:29:43 2008 +1100 +++ b/kernel/workqueue.c Fri Oct 24 01:16:52 2008 +1100 @@ -970,6 +970,51 @@ undo: return ret; } +#ifdef CONFIG_SMP +struct work_for_cpu { + struct work_struct work; + long (*fn)(void *); + void *arg; + long ret; +}; + +static void do_work_for_cpu(struct work_struct *w) +{ + struct work_for_cpu *wfc = container_of(w, struct work_for_cpu, work); + + wfc->ret = wfc->fn(wfc->arg); +} + +/** + * work_on_cpu - run a function in user context on a particular cpu + * @cpu: the cpu to run on + * @fn: the function to run + * @arg: the function arg + * + * This will return -EINVAL in the cpu is not online, or the return value + * of @fn otherwise. + */ +long work_on_cpu(unsigned int cpu, long (*fn)(void *), void *arg) +{ + struct work_for_cpu wfc; + + INIT_WORK(&wfc.work, do_work_for_cpu); + wfc.fn = fn; + wfc.arg = arg; + get_online_cpus(); + if (unlikely(!cpu_online(cpu))) + wfc.ret = -EINVAL; + else { + schedule_work_on(cpu, &wfc.work); + flush_workqueue(&wfc.work); + } + put_online_cpus(); + + return wfc.ret; +} +EXPORT_SYMBOL_GPL(work_on_cpu); +#endif /* CONFIG_SMP */ + void __init init_workqueues(void) { cpu_populated_map = cpu_online_map; -- 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/