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[2620:137:e000::1:20]) by mx.google.com with ESMTP id vv1-20020a170907a68100b0093626311338si27291388ejc.936.2023.03.30.05.25.20; Thu, 30 Mar 2023 05:25:46 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=QUARANTINE sp=QUARANTINE dis=NONE) header.from=huawei.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231482AbjC3MO2 (ORCPT + 99 others); Thu, 30 Mar 2023 08:14:28 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45168 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231463AbjC3MO1 (ORCPT ); Thu, 30 Mar 2023 08:14:27 -0400 Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2CE5A5240 for ; Thu, 30 Mar 2023 05:14:26 -0700 (PDT) Received: from dggpemm500013.china.huawei.com (unknown [172.30.72.55]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4PnMhV0k1RzgZgq; Thu, 30 Mar 2023 20:11:06 +0800 (CST) Received: from ubuntu1804.huawei.com (10.67.175.36) by dggpemm500013.china.huawei.com (7.185.36.172) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.21; Thu, 30 Mar 2023 20:14:23 +0800 From: Chen Zhongjin To: CC: , , , , , , , , , , , , , Subject: [PATCH] wchan: Fix get_wchan() when task in schedule Date: Thu, 30 Mar 2023 20:12:37 +0800 Message-ID: <20230330121238.176534-1-chenzhongjin@huawei.com> X-Mailer: git-send-email 2.17.1 MIME-Version: 1.0 X-Originating-IP: [10.67.175.36] X-ClientProxiedBy: dggems703-chm.china.huawei.com (10.3.19.180) To dggpemm500013.china.huawei.com (7.185.36.172) X-CFilter-Loop: Reflected X-Spam-Status: No, score=-2.3 required=5.0 tests=RCVD_IN_DNSWL_MED, SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1761795528479281274?= X-GMAIL-MSGID: =?utf-8?q?1761795528479281274?= get_wchan() check task to unwind is not running or going to run by: state != TASK_RUNNING && state != TASK_WAKING && !p->on_rq However this cannot detect task which is going to be scheduled out. For example, in this path: __wait_for_common(x, schedule_timeout, timeout, TASK_UNINTERRUPTIBLE) do_wait_for_common() // state == TASK_UNINTERRUPTIBLE schedule_timeout() __schedule() deactivate_task() // on_rq = 0 After this point get_wchan() can be run on the task but it is still running actually, and p->pi_lock doesn't work for this case. It can trigger some warning when running stacktrace on a running task. Also check p->on_cpu to promise task is really switched out can prevent this. Fixes: 42a20f86dc19 ("sched: Add wrapper for get_wchan() to keep task blocked") Signed-off-by: Chen Zhongjin --- kernel/sched/core.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 0d18c3969f90..2071d1c0eaca 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -2041,7 +2041,8 @@ unsigned long get_wchan(struct task_struct *p) raw_spin_lock_irq(&p->pi_lock); state = READ_ONCE(p->__state); smp_rmb(); /* see try_to_wake_up() */ - if (state != TASK_RUNNING && state != TASK_WAKING && !p->on_rq) + if (state != TASK_RUNNING && state != TASK_WAKING && + !p->on_rq && !p->on_cpu) ip = __get_wchan(p); raw_spin_unlock_irq(&p->pi_lock);