Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755254Ab3H2OC1 (ORCPT ); Thu, 29 Aug 2013 10:02:27 -0400 Received: from szxga03-in.huawei.com ([119.145.14.66]:20574 "EHLO szxga03-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755168Ab3H2OCZ (ORCPT ); Thu, 29 Aug 2013 10:02:25 -0400 From: Libin To: , , , , , , , , , , , CC: , , , , , , Subject: [PATCH 11/14] trace: Fix invalid wakeup in wait_to_die Date: Thu, 29 Aug 2013 21:57:46 +0800 Message-ID: <1377784669-28140-12-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: 2012 Lines: 66 If thread is preempted before calling set_current_state(TASK_INTERRUPTIBLE), and the other thread set the condition(kthread_stop). After that when this thread 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. ------------- wait_to_die() ------------- set_current_state(TASK_INTERRUPTIBLE); while (!kthread_should_stop()) { schedule(); set_current_state(TASK_INTERRUPTIBLE); } __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. ------------- wait_to_die() ------------- preempt_disable(); set_current_state(TASK_INTERRUPTIBLE); while (!kthread_should_stop()) { preempt_enable(); schedule(); preempt_disable(); set_current_state(TASK_INTERRUPTIBLE); } __set_current_state(TASK_RUNNING); preempt_enable(); Signed-off-by: Libin --- kernel/trace/ring_buffer_benchmark.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/kernel/trace/ring_buffer_benchmark.c b/kernel/trace/ring_buffer_benchmark.c index a5457d5..3c0bc03 100644 --- a/kernel/trace/ring_buffer_benchmark.c +++ b/kernel/trace/ring_buffer_benchmark.c @@ -359,12 +359,16 @@ static void ring_buffer_producer(void) static void wait_to_die(void) { + preempt_disable(); set_current_state(TASK_INTERRUPTIBLE); while (!kthread_should_stop()) { + preempt_enable(); schedule(); + preempt_disable(); set_current_state(TASK_INTERRUPTIBLE); } __set_current_state(TASK_RUNNING); + preempt_enable(); } static int ring_buffer_consumer_thread(void *arg) -- 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/