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=-13.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable 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 24942C49EAB for ; Sat, 26 Jun 2021 13:06:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0259961584 for ; Sat, 26 Jun 2021 13:06:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230398AbhFZNIb (ORCPT ); Sat, 26 Jun 2021 09:08:31 -0400 Received: from mail.kernel.org ([198.145.29.99]:33858 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230097AbhFZNIB (ORCPT ); Sat, 26 Jun 2021 09:08:01 -0400 Received: from gandalf.local.home (cpe-66-24-58-225.stny.res.rr.com [66.24.58.225]) (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 B73C261C37; Sat, 26 Jun 2021 13:05:38 +0000 (UTC) Received: from rostedt by gandalf.local.home with local (Exim 4.94.2) (envelope-from ) id 1lx809-000EnH-Pc; Sat, 26 Jun 2021 09:05:37 -0400 Message-ID: <20210626130537.639504615@goodmis.org> User-Agent: quilt/0.66 Date: Sat, 26 Jun 2021 09:04:21 -0400 From: Steven Rostedt To: linux-kernel@vger.kernel.org Cc: Ingo Molnar , Andrew Morton , Phil Auld , Sebastian Andrzej Siewior , Kate Carcia , 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, Daniel Bristot de Oliveira Subject: [for-next][PATCH 17/24] trace/hwlat: Remove printk from sampling loop References: <20210626130404.033700863@goodmis.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Daniel Bristot de Oliveira 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. Link: https://lkml.kernel.org/r/9d77c34869748aa105e965c769d24642914eea3a.1624372313.git.bristot@redhat.com Cc: Phil Auld Cc: Sebastian Andrzej Siewior Cc: Kate Carcia Cc: Jonathan Corbet 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 Signed-off-by: Steven Rostedt (VMware) --- 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 44f46bc1140f..a625bfdb844e 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; } -- 2.30.2