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=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED 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 970A6C4360F for ; Thu, 4 Apr 2019 01:38:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6C16B2147C for ; Thu, 4 Apr 2019 01:38:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726880AbfDDBiN (ORCPT ); Wed, 3 Apr 2019 21:38:13 -0400 Received: from mail.kernel.org ([198.145.29.99]:36290 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726559AbfDDBhr (ORCPT ); Wed, 3 Apr 2019 21:37:47 -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 9512821855; Thu, 4 Apr 2019 01:37:46 +0000 (UTC) Received: from rostedt by gandalf.local.home with local (Exim 4.92) (envelope-from ) id 1hBrK5-00053k-NQ; Wed, 03 Apr 2019 21:37:45 -0400 Message-Id: <20190404013745.616653252@goodmis.org> User-Agent: quilt/0.65 Date: Wed, 03 Apr 2019 21:37:36 -0400 From: Steven Rostedt To: linux-kernel@vger.kernel.org Cc: Ingo Molnar , Andrew Morton , Masami Hiramatsu , Namhyung Kim , Tom Zanussi Subject: [for-next][PATCH 15/19] tracing: Add tracing/error_log Documentation References: <20190404013721.023858792@goodmis.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Tom Zanussi Move most of the hist trigger extended error documentation to ftrace.rst and expand on it to fully document tracing/error_log. Link: http://lkml.kernel.org/r/c5d53c8f643ef6844d6ad8d0200c116936730b01.1554072478.git.tom.zanussi@linux.intel.com Acked-by: Masami Hiramatsu Acked-by: Namhyung Kim Signed-off-by: Tom Zanussi Signed-off-by: Steven Rostedt (VMware) --- Documentation/trace/ftrace.rst | 31 +++++++++++++++++++++++++++++++ Documentation/trace/histogram.rst | 16 ++-------------- 2 files changed, 33 insertions(+), 14 deletions(-) diff --git a/Documentation/trace/ftrace.rst b/Documentation/trace/ftrace.rst index 7c5e6d6ab5d1..809b39d066ee 100644 --- a/Documentation/trace/ftrace.rst +++ b/Documentation/trace/ftrace.rst @@ -765,6 +765,37 @@ Here is the list of current tracers that may be configured. tracers from tracing simply echo "nop" into current_tracer. +Error conditions +---------------- + + For most ftrace commands, failure modes are obvious and communicated + using standard return codes. + + For other more involved commands, extended error information may be + available via the tracing/error_log file. For the commands that + support it, reading the tracing/error_log file after an error will + display more detailed information about what went wrong, if + information is available. The tracing/error_log file is a circular + error log displaying a small number (currently, 8) of ftrace errors + for the last (8) failed commands. + + The extended error information and usage takes the form shown in + this example:: + + # echo xxx > /sys/kernel/debug/tracing/events/sched/sched_wakeup/trigger + echo: write error: Invalid argument + + # cat /sys/kernel/debug/tracing/error_log + [ 5348.887237] location: error: Couldn't yyy: zzz + Command: xxx + ^ + [ 7517.023364] location: error: Bad rrr: sss + Command: ppp qqq + ^ + + To clear the error log, echo the empty string into it:: + + # echo > /sys/kernel/debug/tracing/error_log Examples of using the tracer ---------------------------- diff --git a/Documentation/trace/histogram.rst b/Documentation/trace/histogram.rst index 0ea59d45aef1..7612c7ad5715 100644 --- a/Documentation/trace/histogram.rst +++ b/Documentation/trace/histogram.rst @@ -199,20 +199,8 @@ Extended error information For some error conditions encountered when invoking a hist trigger command, extended error information is available via the - corresponding event's 'hist' file. Reading the hist file after an - error will display more detailed information about what went wrong, - if information is available. This extended error information will - be available until the next hist trigger command for that event. - - If available for a given error condition, the extended error - information and usage takes the following form:: - - # echo xxx > /sys/kernel/debug/tracing/events/sched/sched_wakeup/trigger - echo: write error: Invalid argument - - # cat /sys/kernel/debug/tracing/events/sched/sched_wakeup/hist - ERROR: Couldn't yyy: zzz - Last command: xxx + tracing/error_log file. See Error Conditions in + :file:`Documentation/trace/ftrace.rst` for details. 6.2 'hist' trigger examples --------------------------- -- 2.20.1