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=-0.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,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 2A1A1C433E0 for ; Thu, 18 Jun 2020 12:55:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E73DD206F7 for ; Thu, 18 Jun 2020 12:54:59 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="GfvYVDcC" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729955AbgFRMy6 (ORCPT ); Thu, 18 Jun 2020 08:54:58 -0400 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:46536 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726909AbgFRMyy (ORCPT ); Thu, 18 Jun 2020 08:54:54 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1592484893; 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=v9FbjWBdAd7q99k+gAtkUvgrScXCggI31g4H1SHIHlE=; b=GfvYVDcCmbLqnv7cHoHE325+ggIBc26DLjM28bMFPOO7ElIsEvHXyn0epURZd3MJqQaFWF 5WzKJfWVKgVHOOrrm08yrfWHYqAAgg/7cf7+zs0Nsvi/AeFsFZbmSwelWVCQ8B7E3iLSs4 Uew6e5XA51Kc6VZktWTlNUC4KnhvoOA= 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-299-ozpWvtOxPhqpPeYZMlbwrw-1; Thu, 18 Jun 2020 08:54:51 -0400 X-MC-Unique: ozpWvtOxPhqpPeYZMlbwrw-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id CDE5A835B42; Thu, 18 Jun 2020 12:54:49 +0000 (UTC) Received: from T590 (ovpn-13-98.pek2.redhat.com [10.72.13.98]) by smtp.corp.redhat.com (Postfix) with ESMTPS id D11585D9E5; Thu, 18 Jun 2020 12:54:42 +0000 (UTC) Date: Thu, 18 Jun 2020 20:54:38 +0800 From: Ming Lei To: Ming Lei Cc: "Naveen N. Rao" , Anil S Keshavamurthy , Linux Kernel Mailing List , "David S. Miller" , Masami Hiramatsu , Steven Rostedt , linux-block Subject: Re: kprobe: __blkdev_put probe is missed Message-ID: <20200618125438.GA191266@T590> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jun 17, 2020 at 06:30:39PM +0800, Ming Lei wrote: > Hello Guys, > > I found probe on __blkdev_put is missed, which can be observed > via bcc/perf reliably: > > 1) start trace > - perf probe __blkdev_put > - perf trace -a -e probe:__blkdev_put > > or > > /usr/share/bcc/tools/stackcount __blkdev_put > > 2) run the following command: > blockdev --getbsz /dev/sda1 > > 3) 'perf trace' or stackcount just dumps one trace event, and it > should have been two > __blkdev_put() traces, since one __blkdev_put() is called for > partition(/dev/sda1), > and another is for disk(/dev/sda). If trace_printk() is added in __blkdev_put(), > two events will be captured from ftrace. > The issue can be shown by loading a kprobe module which registers on __blkdev_put(), just by replacing _do_fork with __blkdev_put on samples/kprobes/kprobe_example.c. So the issue is really in kprobe code. Thanks, Ming