From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_PASS,T_DKIMWL_WL_HIGH,URIBL_BLOCKED, USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0E084ECDFB0 for ; Fri, 13 Jul 2018 16:28:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BA97C20850 for ; Fri, 13 Jul 2018 16:28:41 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="0JTEa0GJ" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BA97C20850 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731956AbeGMQoA (ORCPT ); Fri, 13 Jul 2018 12:44:00 -0400 Received: from mail.kernel.org ([198.145.29.99]:47348 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729622AbeGMQoA (ORCPT ); Fri, 13 Jul 2018 12:44:00 -0400 Received: from localhost.localdomain (NE2965lan1.rev.em-net.ne.jp [210.141.244.193]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 9626D20850; Fri, 13 Jul 2018 16:28:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1531499318; bh=ZmQGJMHOih9M0KNB61xjV675a9eoetqcRTa0LzDn0RY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=0JTEa0GJ1nvgbPUISuf0QIAXR0SSgI/PwHsNGGb1azFz+UTuK15Zwc3lNn8FztgV6 HHzpJ0bxnHVpVC6p9qkN1fL/Ad7r21Aid2iWqlQVFXxIST4UQOWgrNUd4/kMGDzkXN eSkAUUvlO20Lp3IFSD/Dgj0WUv5h3cAD+mIvjOrg= From: Masami Hiramatsu To: Steven Rostedt Cc: Ingo Molnar , Shuah Khan , Masami Hiramatsu , Tom Zanussi , Hiraku Toyooka , linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: [PATCH 2/3] [BUGFIX] ring_buffer: tracing: Inherit the tracing setting to next ring buffer Date: Sat, 14 Jul 2018 01:28:15 +0900 Message-Id: <153149929558.11274.11730609978254724394.stgit@devbox> X-Mailer: git-send-email 2.13.6 In-Reply-To: <153149923649.11274.14970833360963898112.stgit@devbox> References: <153149923649.11274.14970833360963898112.stgit@devbox> User-Agent: StGit/0.17.1-dirty MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Inherit the tracing on/off setting on ring_buffer to next trace buffer when taking a snapshot. Taking a snapshot is done by swapping with backup ring buffer (max_tr_buffer). But since the tracing on/off setting is set in the ring buffer, when swapping it, tracing on/off setting can also be changed. This causes a strange result like below; /sys/kernel/debug/tracing # cat tracing_on 1 /sys/kernel/debug/tracing # echo 0 > tracing_on /sys/kernel/debug/tracing # echo 1 > snapshot /sys/kernel/debug/tracing # cat tracing_on 1 /sys/kernel/debug/tracing # echo 1 > snapshot /sys/kernel/debug/tracing # cat tracing_on 0 We don't touch tracing_on, but snapshot changes tracing_on setting each time. This must be a bug, because user never know that each "ring_buffer" stores tracing-enable state and snapshot is done by swapping ring buffers. This patch fixes above strange behavior. Fixes: commit debdd57f5145 ("tracing: Make a snapshot feature available from userspace") Signed-off-by: Masami Hiramatsu Cc: Steven Rostedt Cc: Ingo Molnar Cc: Hiraku Toyooka Cc: stable@vger.kernel.org --- include/linux/ring_buffer.h | 1 + kernel/trace/ring_buffer.c | 12 ++++++++++++ kernel/trace/trace.c | 6 ++++++ 3 files changed, 19 insertions(+) diff --git a/include/linux/ring_buffer.h b/include/linux/ring_buffer.h index b72ebdff0b77..003d09ab308d 100644 --- a/include/linux/ring_buffer.h +++ b/include/linux/ring_buffer.h @@ -165,6 +165,7 @@ void ring_buffer_record_enable(struct ring_buffer *buffer); void ring_buffer_record_off(struct ring_buffer *buffer); void ring_buffer_record_on(struct ring_buffer *buffer); int ring_buffer_record_is_on(struct ring_buffer *buffer); +int ring_buffer_record_is_set_on(struct ring_buffer *buffer); void ring_buffer_record_disable_cpu(struct ring_buffer *buffer, int cpu); void ring_buffer_record_enable_cpu(struct ring_buffer *buffer, int cpu); diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 6a46af21765c..4038ed74ab95 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -3227,6 +3227,18 @@ int ring_buffer_record_is_on(struct ring_buffer *buffer) } /** + * ring_buffer_record_is_set_on - return true if the ring buffer is set writable + * @buffer: The ring buffer to see if write is set enabled + * + * Returns true if the ring buffer is set writable by ring_buffer_record_on(). + * Note that this does NOT mean it is in a writable state. + */ +int ring_buffer_record_is_set_on(struct ring_buffer *buffer) +{ + return !(atomic_read(&buffer->record_disabled) & RB_BUFFER_OFF); +} + +/** * ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer * @buffer: The ring buffer to stop writes to. * @cpu: The CPU buffer to stop diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 2556d8c097d2..bbd5a94a7ef1 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -1378,6 +1378,12 @@ update_max_tr(struct trace_array *tr, struct task_struct *tsk, int cpu) arch_spin_lock(&tr->max_lock); + /* Inherit the recordable setting from trace_buffer */ + if (ring_buffer_record_is_set_on(tr->trace_buffer.buffer)) + ring_buffer_record_on(tr->max_buffer.buffer); + else + ring_buffer_record_off(tr->max_buffer.buffer); + swap(tr->trace_buffer.buffer, tr->max_buffer.buffer); __update_max_tr(tr, tsk, cpu);