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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT 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 7B0CDC282C0 for ; Fri, 25 Jan 2019 04:32:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 49ED3218DE for ; Fri, 25 Jan 2019 04:32:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727772AbfAYEcI (ORCPT ); Thu, 24 Jan 2019 23:32:08 -0500 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:57048 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726147AbfAYEcH (ORCPT ); Thu, 24 Jan 2019 23:32:07 -0500 Received: from pps.filterd (m0098420.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.27/8.16.0.27) with SMTP id x0P4T6MY194658 for ; Thu, 24 Jan 2019 23:32:06 -0500 Received: from e15.ny.us.ibm.com (e15.ny.us.ibm.com [129.33.205.205]) by mx0b-001b2d01.pphosted.com with ESMTP id 2q7tc5thb5-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Thu, 24 Jan 2019 23:32:06 -0500 Received: from localhost by e15.ny.us.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) Fri, 25 Jan 2019 04:32:01 -0000 Received: from b01ledav003.gho.pok.ibm.com (b01ledav003.gho.pok.ibm.com [9.57.199.108]) by b01cxnp23032.gho.pok.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x0P4W0AB20250804 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Fri, 25 Jan 2019 04:32:00 GMT Received: from b01ledav003.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 08A32B2066; Fri, 25 Jan 2019 04:32:00 +0000 (GMT) Received: from b01ledav003.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id B59A3B205F; Fri, 25 Jan 2019 04:31:59 +0000 (GMT) Received: from paulmck-ThinkPad-W541 (unknown [9.80.206.63]) by b01ledav003.gho.pok.ibm.com (Postfix) with ESMTP; Fri, 25 Jan 2019 04:31:59 +0000 (GMT) Received: by paulmck-ThinkPad-W541 (Postfix, from userid 1000) id 95F5D16C64CE; Thu, 24 Jan 2019 20:31:58 -0800 (PST) Date: Thu, 24 Jan 2019 20:31:58 -0800 From: "Paul E. McKenney" To: Alexei Starovoitov Cc: Alexei Starovoitov , Jann Horn , Peter Zijlstra , Alexei Starovoitov , "David S. Miller" , Daniel Borkmann , "jakub.kicinski@netronome.com" , Network Development , Kernel Team , Ingo Molnar , Will Deacon Subject: Re: [PATCH v4 bpf-next 1/9] bpf: introduce bpf_spin_lock Reply-To: paulmck@linux.ibm.com References: <20190124041403.2100609-1-ast@kernel.org> <20190124041403.2100609-2-ast@kernel.org> <20190124180109.GA27771@hirez.programming.kicks-ass.net> <20190124185652.GB17767@hirez.programming.kicks-ass.net> <20190124234232.GY4240@linux.ibm.com> <20190125000515.jizijxz4n735gclx@ast-mbp.dhcp.thefacebook.com> <20190125012224.GZ4240@linux.ibm.com> <20190125023816.zolpqls5bcsbqsga@ast-mbp.dhcp.thefacebook.com> <150dc5d3-21c3-bbb6-6e5b-2ab8ab0e3f38@fb.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <150dc5d3-21c3-bbb6-6e5b-2ab8ab0e3f38@fb.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-GCONF: 00 x-cbid: 19012504-0068-0000-0000-000003886E60 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00010472; HX=3.00000242; KW=3.00000007; PH=3.00000004; SC=3.00000277; SDB=6.01151392; UDB=6.00600108; IPR=6.00931736; MB=3.00025278; MTD=3.00000008; XFM=3.00000015; UTC=2019-01-25 04:32:03 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19012504-0069-0000-0000-000047428210 Message-Id: <20190125043158.GB4240@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-01-25_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=8.0.1-1810050000 definitions=main-1901250034 Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Fri, Jan 25, 2019 at 04:27:02AM +0000, Alexei Starovoitov wrote: > On 1/24/19 6:38 PM, Alexei Starovoitov wrote: > >> For programs created with CAP_SYS_ADMIN, > >> things get more tricky because you can create your own functions and > >> call them repeatedly; I'm not sure whether the pessimal runtime there > >> becomes exponential, or whether there is some check that catches this. > > I think you're referring to bpf-to-bpf calls. > > The limit it still the same. 4k per program including all calls. > > tail calls are not allowed when bpf-to-bpf is used. So no 32 multiplier. > > Jann, > > I think you meant > main: > call A > call A > call A > exit > A: > call B > call B > call B > exit > B: > call C > ... > > scenario when everything fits into 4k? > Would be great if you can construct such test while we're fixing > the rest of the issues brought up in this thread. > It will definitely be no more than BPF_COMPLEXITY_LIMIT_INSNS > which is 128k, but I wonder what will be the actual number of > executed insns. > I think such clever constructed sequence can actually > hit 128k executed too. > It would be awesome test to add to test_verifier.c > We have some of such pushing-the-boundary tests in lib/test_bpf.c > that are generated in assembler. > The longest takes 23853 nanoseconds, but clever bpf2bpf call hack > like above with map_update call in the leaf function should > certainly take much longer. > I accept Paul's challenge to try to get such fancy bpf prog > to take 100 millseconds :) Fair enough! But once you meet my challenge, the RCU CPU stall warning code will challenge you to hit 21 seconds (or only three seconds given an appropriately configured kernel). ;-) Thanx, Paul