From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1161656AbWAMDXE (ORCPT ); Thu, 12 Jan 2006 22:23:04 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1161661AbWAMDTo (ORCPT ); Thu, 12 Jan 2006 22:19:44 -0500 Received: from 216-99-217-87.dsl.aracnet.com ([216.99.217.87]:61058 "EHLO sorel.sous-sol.org") by vger.kernel.org with ESMTP id S1161656AbWAMDT2 (ORCPT ); Thu, 12 Jan 2006 22:19:28 -0500 Message-Id: <20060113032243.154673000@sorel.sous-sol.org> References: <20060113032102.154909000@sorel.sous-sol.org> Date: Thu, 12 Jan 2006 18:37:45 -0800 From: Chris Wright To: linux-kernel@vger.kernel.org, stable@kernel.org, torvalds@osdl.org Cc: Justin Forbes , Zwane Mwaikambo , "Theodore Ts'o" , Randy Dunlap , Dave Jones , Chuck Wolber , akpm@osdl.org, alan@lxorguk.ukuu.org.uk, ntl@pobox.com Subject: [PATCH 07/17] [PATCH] fix workqueue oops during cpu offline Content-Disposition: inline; filename=fix-workqueue-oops-during-cpu-offline.patch Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org -stable review patch. If anyone has any objections, please let us know. ------------------ Use first_cpu(cpu_possible_map) for the single-thread workqueue case. We used to hardcode 0, but that broke on systems where !cpu_possible(0) when workqueue_struct->cpu_workqueue_struct was changed from a static array to alloc_percpu. Commit id bce61dd49d6ba7799be2de17c772e4c701558f14 ("Fix hardcoded cpu=0 in workqueue for per_cpu_ptr() calls") fixed that for Ben's funky sparc64 system, but it regressed my Power5. Offlining cpu 0 oopses upon the next call to queue_work for a single-thread workqueue, because now we try to manipulate per_cpu_ptr(wq->cpu_wq, 1), which is uninitialized. So we need to establish an unchanging "slot" for single-thread workqueues which will have a valid percpu allocation. Since alloc_percpu keys off of cpu_possible_map, which must not change after initialization, make this slot == first_cpu(cpu_possible_map). Signed-off-by: Nathan Lynch Cc: Signed-off-by: Andrew Morton Signed-off-by: Chris Wright --- kernel/workqueue.c | 16 ++++++++++------ 1 files changed, 10 insertions(+), 6 deletions(-) Index: linux-2.6.15.y/kernel/workqueue.c =================================================================== --- linux-2.6.15.y.orig/kernel/workqueue.c +++ linux-2.6.15.y/kernel/workqueue.c @@ -29,7 +29,8 @@ #include /* - * The per-CPU workqueue (if single thread, we always use cpu 0's). + * The per-CPU workqueue (if single thread, we always use the first + * possible cpu). * * The sequence counters are for flush_scheduled_work(). It wants to wait * until until all currently-scheduled works are completed, but it doesn't @@ -69,6 +70,8 @@ struct workqueue_struct { static DEFINE_SPINLOCK(workqueue_lock); static LIST_HEAD(workqueues); +static int singlethread_cpu; + /* If it's single threaded, it isn't in the list of workqueues. */ static inline int is_single_threaded(struct workqueue_struct *wq) { @@ -102,7 +105,7 @@ int fastcall queue_work(struct workqueue if (!test_and_set_bit(0, &work->pending)) { if (unlikely(is_single_threaded(wq))) - cpu = any_online_cpu(cpu_online_map); + cpu = singlethread_cpu; BUG_ON(!list_empty(&work->entry)); __queue_work(per_cpu_ptr(wq->cpu_wq, cpu), work); ret = 1; @@ -118,7 +121,7 @@ static void delayed_work_timer_fn(unsign int cpu = smp_processor_id(); if (unlikely(is_single_threaded(wq))) - cpu = any_online_cpu(cpu_online_map); + cpu = singlethread_cpu; __queue_work(per_cpu_ptr(wq->cpu_wq, cpu), work); } @@ -267,7 +270,7 @@ void fastcall flush_workqueue(struct wor if (is_single_threaded(wq)) { /* Always use first cpu's area. */ - flush_cpu_workqueue(per_cpu_ptr(wq->cpu_wq, any_online_cpu(cpu_online_map))); + flush_cpu_workqueue(per_cpu_ptr(wq->cpu_wq, singlethread_cpu)); } else { int cpu; @@ -320,7 +323,7 @@ struct workqueue_struct *__create_workqu lock_cpu_hotplug(); if (singlethread) { INIT_LIST_HEAD(&wq->list); - p = create_workqueue_thread(wq, any_online_cpu(cpu_online_map)); + p = create_workqueue_thread(wq, singlethread_cpu); if (!p) destroy = 1; else @@ -374,7 +377,7 @@ void destroy_workqueue(struct workqueue_ /* We don't need the distraction of CPUs appearing and vanishing. */ lock_cpu_hotplug(); if (is_single_threaded(wq)) - cleanup_workqueue_thread(wq, any_online_cpu(cpu_online_map)); + cleanup_workqueue_thread(wq, singlethread_cpu); else { for_each_online_cpu(cpu) cleanup_workqueue_thread(wq, cpu); @@ -543,6 +546,7 @@ static int __devinit workqueue_cpu_callb void init_workqueues(void) { + singlethread_cpu = first_cpu(cpu_possible_map); hotcpu_notifier(workqueue_cpu_callback, 0); keventd_wq = create_workqueue("events"); BUG_ON(!keventd_wq); --