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=-15.9 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 8FBDDC48BE5 for ; Tue, 15 Jun 2021 09:29:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7479C61446 for ; Tue, 15 Jun 2021 09:29:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231488AbhFOJb5 (ORCPT ); Tue, 15 Jun 2021 05:31:57 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:45994 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231491AbhFOJbw (ORCPT ); Tue, 15 Jun 2021 05:31:52 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1623749388; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=oZVlLGY0kqQAYmVdD+6nEDNmFy2iD2bHg+txa/b3qk8=; b=MY6mc6h4umwaSFpK6efuz8T9HM1KzxrPZEwQC64ELcT7XMALOdKNy9C8OhiQ6tQYoIFwVv ZG/OJeW8RrR13ScqKzLF59sTv6XoTGJqYl27vAb3oOSEFdV7B2T5f3ETjDXdt4l2Vm3ahX DcuThrPgQJqdtl75GAM9s/wrOkmhYaI= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-445-NaBsZni7PTKROpxqWbz96Q-1; Tue, 15 Jun 2021 05:29:46 -0400 X-MC-Unique: NaBsZni7PTKROpxqWbz96Q-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 2D359100C660; Tue, 15 Jun 2021 09:29:45 +0000 (UTC) Received: from x1.com (ovpn-113-40.rdu2.redhat.com [10.10.113.40]) by smtp.corp.redhat.com (Postfix) with ESMTP id B2E1D5D6AD; Tue, 15 Jun 2021 09:29:40 +0000 (UTC) From: Daniel Bristot de Oliveira To: Steven Rostedt Cc: Phil Auld , Sebastian Andrzej Siewior , Kate Carcia , Daniel Bristot de Oliveira , Jonathan Corbet , Ingo Molnar , Peter Zijlstra , Thomas Gleixner , Alexandre Chartre , Clark Willaims , John Kacur , Juri Lelli , Borislav Petkov , "H. Peter Anvin" , x86@kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH V4 08/12] trace/hwlat: Remove printk from sampling loop Date: Tue, 15 Jun 2021 11:28:47 +0200 Message-Id: In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org hwlat has some time operation checks on the sample loop, and it is currently using pr_err (printk) to report them. The problem is that this can lead the system to an unresponsible state due to an overflow of printk messages. This problem can be mitigated by writing the error message to the trace buffer. Remove the printk messages from the sampling loop, switching the to messages in the trace buffer. No functional change. Cc: Jonathan Corbet Cc: Steven Rostedt Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Alexandre Chartre Cc: Clark Willaims Cc: John Kacur Cc: Juri Lelli Cc: Borislav Petkov Cc: "H. Peter Anvin" Cc: x86@kernel.org Cc: linux-doc@vger.kernel.org Cc: linux-kernel@vger.kernel.org Signed-off-by: Daniel Bristot de Oliveira --- kernel/trace/trace_hwlat.c | 15 ++++++++++++--- 1 file changed, 12 insertions(+), 3 deletions(-) diff --git a/kernel/trace/trace_hwlat.c b/kernel/trace/trace_hwlat.c index 0ab6acf6ae9a..86e8541d4331 100644 --- a/kernel/trace/trace_hwlat.c +++ b/kernel/trace/trace_hwlat.c @@ -182,6 +182,15 @@ void trace_hwlat_callback(bool enter) kdata->nmi_count++; } +/* + * hwlat_err - report a hwlat error. + */ +#define hwlat_err(msg) ({ \ + struct trace_array *tr = hwlat_trace; \ + \ + trace_array_printk_buf(tr->array_buffer.buffer, _THIS_IP_, msg); \ +}) + /** * get_sample - sample the CPU TSC and look for likely hardware latencies * @@ -225,7 +234,7 @@ static int get_sample(void) outer_diff = time_to_us(time_sub(t1, last_t2)); /* This shouldn't happen */ if (outer_diff < 0) { - pr_err(BANNER "time running backwards\n"); + hwlat_err(BANNER "time running backwards\n"); goto out; } if (outer_diff > outer_sample) @@ -237,7 +246,7 @@ static int get_sample(void) /* Check for possible overflows */ if (total < last_total) { - pr_err("Time total overflowed\n"); + hwlat_err("Time total overflowed\n"); break; } last_total = total; @@ -253,7 +262,7 @@ static int get_sample(void) /* This shouldn't happen */ if (diff < 0) { - pr_err(BANNER "time running backwards\n"); + hwlat_err(BANNER "time running backwards\n"); goto out; } -- 2.31.1