Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755497Ab3H2OEJ (ORCPT ); Thu, 29 Aug 2013 10:04:09 -0400 Received: from szxga03-in.huawei.com ([119.145.14.66]:20515 "EHLO szxga03-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754388Ab3H2OBk (ORCPT ); Thu, 29 Aug 2013 10:01:40 -0400 From: Libin To: , , , , , , , , , , , CC: , , , , , , Subject: [PATCH 14/14] klist: Fix invalid wakeup in klist_remove Date: Thu, 29 Aug 2013 21:57:49 +0800 Message-ID: <1377784669-28140-15-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: 1806 Lines: 73 If thread is preempted before calling set_current_state(TASK_UNINTERRUPTIBLE), and the other thread set the condition followed with wake_up_process. After that when this thread is re-scheduled, calling set_current_state to set itself as state TASK_UNINTERRUPTIBLE, if it is preempted again after that and before __set_current_state(TASK_RUNNING), it triggers the invalid wakeup problem. -------------- klist_remove() -------------- ... for (;;) { set_current_state(TASK_UNINTERRUPTIBLE); if (waiter.woken) break; schedule(); } __set_current_state(TASK_RUNNING); ... 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. -------------- klist_remove() -------------- ... preempt_disable(); for (;;) { set_current_state(TASK_UNINTERRUPTIBLE); if (waiter.woken) break; preempt_enable(); schedule(); preempt_disable(); } __set_current_state(TASK_RUNNING); preempt_enable(); ... Signed-off-by: Libin --- lib/klist.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/lib/klist.c b/lib/klist.c index 358a368..e7c7208 100644 --- a/lib/klist.c +++ b/lib/klist.c @@ -249,13 +249,17 @@ void klist_remove(struct klist_node *n) klist_del(n); + preempt_disable(); for (;;) { set_current_state(TASK_UNINTERRUPTIBLE); if (waiter.woken) break; + preempt_enable(); schedule(); + preempt_disable(); } __set_current_state(TASK_RUNNING); + preempt_enable(); } EXPORT_SYMBOL_GPL(klist_remove); -- 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/