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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 98090C2D0EB for ; Mon, 30 Mar 2020 18:14:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 738A5205ED for ; Mon, 30 Mar 2020 18:14:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727801AbgC3SOm convert rfc822-to-8bit (ORCPT ); Mon, 30 Mar 2020 14:14:42 -0400 Received: from eu-smtp-delivery-151.mimecast.com ([207.82.80.151]:22606 "EHLO eu-smtp-delivery-151.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726017AbgC3SOm (ORCPT ); Mon, 30 Mar 2020 14:14:42 -0400 Received: from AcuMS.aculab.com (156.67.243.126 [156.67.243.126]) (Using TLS) by relay.mimecast.com with ESMTP id uk-mta-228-Uzzyp6fHP5iCb0krCcGUIQ-1; Mon, 30 Mar 2020 19:14:38 +0100 X-MC-Unique: Uzzyp6fHP5iCb0krCcGUIQ-1 Received: from AcuMS.Aculab.com (fd9f:af1c:a25b:0:43c:695e:880f:8750) by AcuMS.aculab.com (fd9f:af1c:a25b:0:43c:695e:880f:8750) with Microsoft SMTP Server (TLS) id 15.0.1347.2; Mon, 30 Mar 2020 19:14:38 +0100 Received: from AcuMS.Aculab.com ([fe80::43c:695e:880f:8750]) by AcuMS.aculab.com ([fe80::43c:695e:880f:8750%12]) with mapi id 15.00.1347.000; Mon, 30 Mar 2020 19:14:38 +0100 From: David Laight To: 'Steven Rostedt' CC: Linux Kernel Mailing List Subject: RE: ftrace not showing the process names for all processes on syscall events Thread-Topic: ftrace not showing the process names for all processes on syscall events Thread-Index: AdYGnj+cWqFtVCqqTmCXgoqvHM5xrf///P+A///qkvCAAEdbAP//7aKg Date: Mon, 30 Mar 2020 18:14:37 +0000 Message-ID: References: <3cdef49951734e83a14959628233d4f0@AcuMS.aculab.com> <20200330110855.437fe854@gandalf.local.home> <7dec110c2dc14792ba744419a4eb907e@AcuMS.aculab.com> <20200330140736.4b5f1667@gandalf.local.home> In-Reply-To: <20200330140736.4b5f1667@gandalf.local.home> Accept-Language: en-GB, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.202.205.107] MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: aculab.com Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Steven Rostedt > Sent: 30 March 2020 19:08 > On Mon, 30 Mar 2020 15:34:08 +0000 > David Laight wrote: > > > Oh, does the 'function_graph' code ignore tail calls? > > Yes and no ;-) It works by dumb luck. As it was a year after function > graph tracing was live (some time in 2010 I believe) that someone brought > up tail calls, and I had to take a look at how it never crashed, and was > surprised that it "just worked". Here's a summary: 'Dumb luck' seems to be failing me :-) I'll look more closely tomorrow. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)