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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS 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 19657C46460 for ; Tue, 14 Aug 2018 04:37:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BE5AE21527 for ; Tue, 14 Aug 2018 04:37:45 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BE5AE21527 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.ibm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731164AbeHNHXG (ORCPT ); Tue, 14 Aug 2018 03:23:06 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:57550 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726079AbeHNHXG (ORCPT ); Tue, 14 Aug 2018 03:23:06 -0400 Received: from pps.filterd (m0098413.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.22/8.16.0.22) with SMTP id w7E4XtEd065727 for ; Tue, 14 Aug 2018 00:37:43 -0400 Received: from e06smtp07.uk.ibm.com (e06smtp07.uk.ibm.com [195.75.94.103]) by mx0b-001b2d01.pphosted.com with ESMTP id 2kuqfq1b2n-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Tue, 14 Aug 2018 00:37:42 -0400 Received: from localhost by e06smtp07.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Tue, 14 Aug 2018 05:37:34 +0100 Received: from d06av26.portsmouth.uk.ibm.com (d06av26.portsmouth.uk.ibm.com [9.149.105.62]) by b06cxnps3074.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id w7E4bXDd42795068 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Tue, 14 Aug 2018 04:37:33 GMT Received: from d06av26.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id C5263AE055; Tue, 14 Aug 2018 07:37:20 +0100 (BST) Received: from d06av26.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 90107AE04D; Tue, 14 Aug 2018 07:37:17 +0100 (BST) Received: from [9.124.35.253] (unknown [9.124.35.253]) by d06av26.portsmouth.uk.ibm.com (Postfix) with ESMTP; Tue, 14 Aug 2018 07:37:17 +0100 (BST) Subject: Re: [PATCH v8 3/6] Uprobes: Support SDT markers having reference count (semaphore) To: Song Liu Cc: Oleg Nesterov , Srikar Dronamraju , Steven Rostedt , mhiramat@kernel.org, Peter Zijlstra , mingo@redhat.com, acme@kernel.org, alexander.shishkin@linux.intel.com, jolsa@redhat.com, namhyung@kernel.org, open list , ananth@linux.vnet.ibm.com, Alexis Berlemont , naveen.n.rao@linux.vnet.ibm.com, linux-arm-kernel@lists.infradead.org, linux-mips@linux-mips.org, linux@armlinux.org.uk, ralf@linux-mips.org, paul.burton@mips.com, Ravi Bangoria References: <20180809041856.1547-1-ravi.bangoria@linux.ibm.com> <20180809041856.1547-4-ravi.bangoria@linux.ibm.com> <95a1221e-aecc-42be-5239-a2c2429be176@linux.ibm.com> <20180813115019.GB28360@redhat.com> <20180813131723.GC28360@redhat.com> From: Ravi Bangoria Date: Tue, 14 Aug 2018 10:07:29 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.8.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 x-cbid: 18081404-0028-0000-0000-000002EA6679 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18081404-0029-0000-0000-000023A384C5 Message-Id: <58d21bac-5a31-85df-4b9f-05815b64f465@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2018-08-14_02:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1807170000 definitions=main-1808140045 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Song, On 08/13/2018 10:42 PM, Song Liu wrote: > On Mon, Aug 13, 2018 at 6:17 AM, Oleg Nesterov wrote: >> On 08/13, Ravi Bangoria wrote: >>> >>>> But damn, process creation (exec) is trivial. We could add a new uprobe_exec() >>>> hook and avoid delayed_uprobe_install() in uprobe_mmap(). >>> >>> I'm sorry. I didn't get this. >> >> Sorry for confusion... >> >> I meant, if only exec*( could race with _register(), we could add another uprobe >> hook which updates all (delayed) counters before return to user-mode. >> >>>> Afaics, the really problematic case is dlopen() which can race with _register() >>>> too, right? >>> >>> dlopen() should internally use mmap() right? So what is the problem here? Can >>> you please elaborate. >> >> What I tried to say is that we can't avoid uprobe_mmap()->delayed_uprobe_install() >> because dlopen() can race with _register() too, just like exec. >> >> Oleg. >> > > How about we do delayed_uprobe_install() per file? Say we keep a list > of delayed_uprobe > in load_elf_binary(). Then we can install delayed_uprobe after loading > all sections of the > file. I'm not sure if I totally understood the idea. But how this approach can solve dlopen() race with _register()? Rather, making delayed_uprobe_list an mm field seems simple and effective idea to me. The only overhead will be list_empty(mm->delayed_list) check. Please let me know if I misunderstood you. Thanks, Ravi