From patchwork Fri Aug 4 12:45:48 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Zheng Yejian X-Patchwork-Id: 13341770 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 49938C00528 for ; Fri, 4 Aug 2023 12:46:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230147AbjHDMqe (ORCPT ); Fri, 4 Aug 2023 08:46:34 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41780 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230054AbjHDMqa (ORCPT ); Fri, 4 Aug 2023 08:46:30 -0400 Received: from szxga08-in.huawei.com (szxga08-in.huawei.com [45.249.212.255]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id F2E1A46B2; Fri, 4 Aug 2023 05:46:28 -0700 (PDT) Received: from dggpeml500012.china.huawei.com (unknown [172.30.72.54]) by szxga08-in.huawei.com (SkyGuard) with ESMTP id 4RHQRP5mPBz1KC70; Fri, 4 Aug 2023 20:45:21 +0800 (CST) Received: from localhost.localdomain (10.67.175.61) by dggpeml500012.china.huawei.com (7.185.36.15) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.27; Fri, 4 Aug 2023 20:46:26 +0800 From: Zheng Yejian To: , , , CC: , , Subject: [PATCH 1/2] tracing: Fix cpu buffers unavailable due to 'record_disabled' messed Date: Fri, 4 Aug 2023 20:45:48 +0800 Message-ID: <20230804124549.2562977-2-zhengyejian1@huawei.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20230804124549.2562977-1-zhengyejian1@huawei.com> References: <20230804124549.2562977-1-zhengyejian1@huawei.com> MIME-Version: 1.0 X-Originating-IP: [10.67.175.61] X-ClientProxiedBy: dggems703-chm.china.huawei.com (10.3.19.180) To dggpeml500012.china.huawei.com (7.185.36.15) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org Trace ring buffer can no longer record anything after executing like: # cd /sys/kernel/tracing # cat tracing_cpumask fff # echo 0 > tracing_cpumask # echo 1 > snapshot # echo fff > tracing_cpumask # echo "hello world" > trace_marker -bash: echo: write error: Bad file descriptor The root cause is that: 1. After `echo 0 > tracing_cpumask`, 'record_disabled' of cpu buffers in 'tr->array_buffer.buffer' became 1 (see tracing_set_cpumask()); 2. After `echo 1 > snapshot`, 'tr->array_buffer.buffer' is swapped with 'tr->max_buffer.buffer', then the 'record_disabled' became 0 (see update_max_tr()); 3. After `echo fff > tracing_cpumask`, the 'record_disabled' become -1; Then array_buffer and max_buffer are both unavailable due to value of 'record_disabled' is not 0. To fix it, enable or disable both array_buffer and max_buffer at the same time in tracing_set_cpumask(). Fixes: 71babb2705e2 ("tracing: change CPU ring buffer state from tracing_cpumask") Signed-off-by: Zheng Yejian --- kernel/trace/trace.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index b8870078ef58..691ec4d4cd19 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -5277,11 +5277,13 @@ int tracing_set_cpumask(struct trace_array *tr, !cpumask_test_cpu(cpu, tracing_cpumask_new)) { atomic_inc(&per_cpu_ptr(tr->array_buffer.data, cpu)->disabled); ring_buffer_record_disable_cpu(tr->array_buffer.buffer, cpu); + ring_buffer_record_disable_cpu(tr->max_buffer.buffer, cpu); } if (!cpumask_test_cpu(cpu, tr->tracing_cpumask) && cpumask_test_cpu(cpu, tracing_cpumask_new)) { atomic_dec(&per_cpu_ptr(tr->array_buffer.data, cpu)->disabled); ring_buffer_record_enable_cpu(tr->array_buffer.buffer, cpu); + ring_buffer_record_enable_cpu(tr->max_buffer.buffer, cpu); } } arch_spin_unlock(&tr->max_lock);