Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756150Ab2JXJ0N (ORCPT ); Wed, 24 Oct 2012 05:26:13 -0400 Received: from mail-da0-f46.google.com ([209.85.210.46]:39573 "EHLO mail-da0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753236Ab2JXJ0K (ORCPT ); Wed, 24 Oct 2012 05:26:10 -0400 From: Huacai Chen To: Ingo Molnar Cc: Peter Zijlstra , linux-kernel@vger.kernel.org, Fuxin Zhang , Huacai Chen Subject: [RFC][PATCH] sched: Fix a deadlock of cpu-hotplug Date: Wed, 24 Oct 2012 17:25:14 +0800 Message-Id: <1351070714-17676-1-git-send-email-chenhc@lemote.com> X-Mailer: git-send-email 1.7.7.3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4744 Lines: 106 We found poweroff sometimes fails on our computers, so we have the lock debug options configured. Then, when we do poweroff or take a cpu down via cpu-hotplug, kernel complain as below. To resove this, we modify sched_ttwu_pending(), disable the local irq when acquire rq->lock. [ 83.066406] ================================= [ 83.066406] [ INFO: inconsistent lock state ] [ 83.066406] 3.5.0-3.lemote #428 Not tainted [ 83.066406] --------------------------------- [ 83.066406] inconsistent {IN-HARDIRQ-W} -> {HARDIRQ-ON-W} usage. [ 83.066406] migration/1/7 [HC0[0]:SC0[0]:HE1:SE1] takes: [ 83.066406] (&rq->lock){?.-.-.}, at: [] sched_ttwu_pending+0x64/0x98 [ 83.066406] {IN-HARDIRQ-W} state was registered at: [ 83.066406] [] __lock_acquire+0x80c/0x1cc0 [ 83.066406] [] lock_acquire+0x60/0x9c [ 83.066406] [] _raw_spin_lock+0x3c/0x50 [ 83.066406] [] scheduler_tick+0x48/0x178 [ 83.066406] [] update_process_times+0x54/0x70 [ 83.066406] [] tick_handle_periodic+0x2c/0x9c [ 83.066406] [] c0_compare_interrupt+0x8c/0x94 [ 83.066406] [] handle_irq_event_percpu+0x7c/0x248 [ 83.066406] [] handle_percpu_irq+0x8c/0xc0 [ 83.066406] [] generic_handle_irq+0x48/0x58 [ 83.066406] [] do_IRQ+0x18/0x24 [ 83.066406] [] mach_irq_dispatch+0xe4/0x124 [ 83.066406] [] ret_from_irq+0x0/0x4 [ 83.066406] [] console_unlock+0x3e8/0x4c0 [ 83.066406] [] con_init+0x370/0x398 [ 83.066406] [] console_init+0x34/0x50 [ 83.066406] [] start_kernel+0x2f8/0x4e0 [ 83.066406] irq event stamp: 971 [ 83.066406] hardirqs last enabled at (971): [] local_flush_tlb_all+0x134/0x17c [ 83.066406] hardirqs last disabled at (970): [] local_flush_tlb_all+0x48/0x17c [ 83.066406] softirqs last enabled at (0): [] copy_process+0x510/0x117c [ 83.066406] softirqs last disabled at (0): [< (null)>] (null) [ 83.066406] [ 83.066406] other info that might help us debug this: [ 83.066406] Possible unsafe locking scenario: [ 83.066406] [ 83.066406] CPU0 [ 83.066406] ---- [ 83.066406] lock(&rq->lock); [ 83.066406] [ 83.066406] lock(&rq->lock); [ 83.066406] [ 83.066406] *** DEADLOCK *** [ 83.066406] [ 83.066406] no locks held by migration/1/7. [ 83.066406] [ 83.066406] stack backtrace: [ 83.066406] Call Trace: [ 83.066406] [] dump_stack+0x8/0x34 [ 83.066406] [] print_usage_bug+0x2ec/0x314 [ 83.066406] [] mark_lock+0x3fc/0x774 [ 83.066406] [] __lock_acquire+0x8a8/0x1cc0 [ 83.066406] [] lock_acquire+0x60/0x9c [ 83.066406] [] _raw_spin_lock+0x3c/0x50 [ 83.066406] [] sched_ttwu_pending+0x64/0x98 [ 83.066406] [] migration_call+0x10c/0x2e0 [ 83.066406] [] notifier_call_chain+0x44/0x94 [ 83.066406] [] __cpu_notify+0x30/0x5c [ 83.066406] [] take_cpu_down+0x5c/0x70 [ 83.066406] [] stop_machine_cpu_stop+0x104/0x1e8 [ 83.066406] [] cpu_stopper_thread+0x110/0x1ac [ 83.066406] [] kthread+0x88/0x90 [ 83.066406] [] kernel_thread_helper+0x10/0x18 Signed-off-by: Huacai Chen --- kernel/sched/core.c | 5 +++-- 1 files changed, 3 insertions(+), 2 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 36e2666..703754a 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -1468,9 +1468,10 @@ static void sched_ttwu_pending(void) { struct rq *rq = this_rq(); struct llist_node *llist = llist_del_all(&rq->wake_list); + unsigned long flags; struct task_struct *p; - raw_spin_lock(&rq->lock); + raw_spin_lock_irqsave(&rq->lock, flags); while (llist) { p = llist_entry(llist, struct task_struct, wake_entry); @@ -1478,7 +1479,7 @@ static void sched_ttwu_pending(void) ttwu_do_activate(rq, p, 0); } - raw_spin_unlock(&rq->lock); + raw_spin_unlock_irqrestore(&rq->lock, flags); } void scheduler_ipi(void) -- 1.7.7.3 -- 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/