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=-7.6 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no 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 2BB32C2D0A8 for ; Mon, 28 Sep 2020 10:08:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DA6ED22204 for ; Mon, 28 Sep 2020 10:08:21 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="ew90q6kP" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726654AbgI1KIV (ORCPT ); Mon, 28 Sep 2020 06:08:21 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:57769 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726513AbgI1KIQ (ORCPT ); Mon, 28 Sep 2020 06:08:16 -0400 Dkim-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1601287695; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=W60elhwFQ/C09jwxL9Ojpt8vM3WLlrkiR3zgT2uDTZI=; b=ew90q6kPTHGfu7FIm16Hl/pdImiu83iNbctEDik+gib5A3nJ1g7bQYEZQjId2RnpOwns5C kKdOhjZsxODs5sxZfyNU0wHmVDAYVaAkBOEQNII0jTtZxPikcP+bJHQxcoPbCWMLBM248c 8QVoDffw0Uik/77Tf8nM5BMp10ch93w= 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-67-PWUQpWqxMQKp6RT7EgfBQA-1; Mon, 28 Sep 2020 06:08:11 -0400 X-MC-Unique: PWUQpWqxMQKp6RT7EgfBQA-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 895A3801AC4; Mon, 28 Sep 2020 10:08:10 +0000 (UTC) Received: from krava (unknown [10.40.193.42]) by smtp.corp.redhat.com (Postfix) with SMTP id 389A37EB74; Mon, 28 Sep 2020 10:08:08 +0000 (UTC) Date: Mon, 28 Sep 2020 12:08:08 +0200 From: Jiri Olsa To: Hagen Paul Pfeifer Cc: linux-kernel@vger.kernel.org, Jiri Olsa , Arnaldo Carvalho de Melo Subject: Re: perf script, libperf: python binding bug (bytearrays vs. strings) Message-ID: <20200928100808.GA3517742@krava> References: <20200927074312.GA3664097@laniakea> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200927074312.GA3664097@laniakea> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Sep 27, 2020 at 09:43:12AM +0200, Hagen Paul Pfeifer wrote: > Hallo Jiri, Arnaldo, > > after updating Debian (probably with the advent of Python 3.8.5, guessing) > I get a wired behavior with python scripting. The error is that the python type > for prev_comm and next_comm are not strings anymore, rather bytearrays. Which > are incompatible types and scripts will not work anymore. NOTE: common_comm is > still fine (see swapper & mutex-thread-co), so they must be treated internal > differently compared to prev_comm and next_comm and possibly show a way to solve > this problem! > > After bisecting the kernel (perf) even back to v5.6 the problem still exist. > Compiling perf with PYTHON=python2 do not show any problems - no problems in > the Python2 world. So I assume with Python 3.8.5 (or other helper library) > something changed internally. I assume the cause exists in perf forever but > is now triggered with the new Python3 version. > > How to reproduce: > > make PYTHON=python3 > ./perf record -e sched:sched_switch -a -- sleep 5 > ./perf script --gen-script py > ./perf script -s ./perf-script.py > > [..] > sched__sched_switch 7 563231.759525792 0 swapper prev_comm=bytearray(b'swapper/7\x00\x00\x00\x00\x00\x00\x00'), prev_pid=0, prev_prio=120, prev_state=, next_comm=bytearray(b'mutex-thread-co\x00'), next_pid=3447985, next_prio=120 > Sample: {addr=0, cpu=7, datasrc=84410401, datasrc_decode=N/A|SNP N/A|TLB N/A|LCK N/A, ip=18446744072189289569, period=1, phys_addr=0, pid=0, tid=0, time=563231759525792, transaction=0, values=[(0, 0)], weight=0} > > sched__sched_switch 7 563231.759582596 3447985 mutex-thread-co prev_comm=bytearray(b'mutex-thread-co\x00'), prev_pid=3447985, prev_prio=120, prev_state=, next_comm=bytearray(b'swapper/7\x00\x00\x00\x00\x00\x00\x00'), next_pid=0, next_prio=120 > Sample: {addr=0, cpu=7, datasrc=84410401, datasrc_decode=N/A|SNP N/A|TLB N/A|LCK N/A, ip=18446744072189289569, period=1, phys_addr=0, pid=3447983, tid=3447985, time=563231759582596, transaction=0, values=[(0, 0)], weight=0} > > > See =bytearray(b'swapper/7\x00\x00\x00\x00\x00\x00\x00') - should be swapper/7 > > > Note: the byte array has the length of 16 - exactly like the kernel > (TASK_COMM_LEN). I assume this is somehow copied directly into the variables > and not stringified anymore. > > > Even worse: I discovered bytearrays which are not correctly "memseted": > bytearray(b'chrome\x00sandbox\x00\x00') > > chrome should be the comm name, but is 'chromesandbox' somehow. See the null > bytes in between. > > Jiri, Arnaldo - I tried to fix this. But the Python binding magic for the > automatically generated events are hard to get comfy. > > Hagen > > PS: assume this fix is also kernel stable relevant. > patch below fixes it for me, but seems strange this was working till now.. maybe you're the only one using this with python3 ;-) jirka --- diff --git a/tools/perf/util/print_binary.c b/tools/perf/util/print_binary.c index 599a1543871d..13fdc51c61d9 100644 --- a/tools/perf/util/print_binary.c +++ b/tools/perf/util/print_binary.c @@ -50,7 +50,7 @@ int is_printable_array(char *p, unsigned int len) len--; - for (i = 0; i < len; i++) { + for (i = 0; i < len && p[i]; i++) { if (!isprint(p[i]) && !isspace(p[i])) return 0; }