Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754876Ab3H2OBu (ORCPT ); Thu, 29 Aug 2013 10:01:50 -0400 Received: from szxga01-in.huawei.com ([119.145.14.64]:9672 "EHLO szxga01-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754253Ab3H2OBs (ORCPT ); Thu, 29 Aug 2013 10:01:48 -0400 From: Libin To: , , , , , , , , , , , CC: , , , , , , Subject: [PATCH 01/14] kthread: Fix invalid wakeup in kthreadd Date: Thu, 29 Aug 2013 21:57:36 +0800 Message-ID: <1377784669-28140-2-git-send-email-huawei.libin@huawei.com> X-Mailer: git-send-email 1.8.1.msysgit.1 In-Reply-To: <1377784669-28140-1-git-send-email-huawei.libin@huawei.com> References: <1377784669-28140-1-git-send-email-huawei.libin@huawei.com> MIME-Version: 1.0 Content-Type: text/plain X-Originating-IP: [10.135.74.57] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2304 Lines: 83 If kthreadd is preempted at(or before) location a, and the other thread, such as calling kthread_create_on_node(), adds a list item to the kthread_create_list followed with wake_up_process(kthread). After that when kthreadd is re-scheduled, calling set_current_state to set itself as state TASK_INTERRUPTIBLE, if it is preempted again after that and before __set_current_state(TASK_RUNNING), it triggers the invalid wakeup problem. ------------------------ kthreadd() ------------------------ ... for (;;) { //location a set_current_state(TASK_INTERRUPTIBLE); if (list_empty(&kthread_create_list)) { //location b schedule(); //location c } __set_current_state(TASK_RUNNING); //location d ... ------------------------ kthread_create_on_node() ------------------------ ... spin_lock(&kthread_create_lock); list_add_tail(&create.list, &kthread_create_list); spin_unlock(&kthread_create_lock); ... wake_up_process(kthreadd_task); ... To solve this problem, using preempt_disable() to bound the operaion that setting the task state and the conditions(set by the wake thread) validation. ------------------------ kthreadd() ------------------------ ... for (;;) { preempt_disable(); set_current_state(TASK_INTERRUPTIBLE); if (list_empty(&kthread_create_list)) { preempt_enable(); schedule(); preempt_disable(); } ... Signed-off-by: Libin --- kernel/kthread.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/kernel/kthread.c b/kernel/kthread.c index 760e86d..25c3fed 100644 --- a/kernel/kthread.c +++ b/kernel/kthread.c @@ -456,10 +456,15 @@ int kthreadd(void *unused) current->flags |= PF_NOFREEZE; for (;;) { + preempt_disable(); set_current_state(TASK_INTERRUPTIBLE); - if (list_empty(&kthread_create_list)) + if (list_empty(&kthread_create_list)) { + preempt_enable(); schedule(); + preempt_disable(); + } __set_current_state(TASK_RUNNING); + preempt_enable(); spin_lock(&kthread_create_lock); while (!list_empty(&kthread_create_list)) { -- 1.8.2.1 -- 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/