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 B2AA0C43381 for ; Wed, 13 Mar 2019 16:37:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7C7CF2171F for ; Wed, 13 Mar 2019 16:37:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726920AbfCMQhR (ORCPT ); Wed, 13 Mar 2019 12:37:17 -0400 Received: from outgoing-auth-1.mit.edu ([18.9.28.11]:50870 "EHLO outgoing.mit.edu" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725856AbfCMQhP (ORCPT ); Wed, 13 Mar 2019 12:37:15 -0400 Received: from callcc.thunk.org (guestnat-104-133-0-99.corp.google.com [104.133.0.99] (may be forged)) (authenticated bits=0) (User authenticated as tytso@ATHENA.MIT.EDU) by outgoing.mit.edu (8.14.7/8.12.4) with ESMTP id x2DGb2Hs003373 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 13 Mar 2019 12:37:02 -0400 Received: by callcc.thunk.org (Postfix, from userid 15806) id DECDC42080E; Wed, 13 Mar 2019 12:37:01 -0400 (EDT) Date: Wed, 13 Mar 2019 12:37:01 -0400 From: "Theodore Ts'o" To: Dmitry Vyukov Cc: Tetsuo Handa , syzbot , syzkaller-bugs , Al Viro , LKML Subject: Re: INFO: rcu detected stall in sys_sendfile64 (2) Message-ID: <20190313163701.GE672@mit.edu> Mail-Followup-To: Theodore Ts'o , Dmitry Vyukov , Tetsuo Handa , syzbot , syzkaller-bugs , Al Viro , LKML References: <00000000000010b2fc057fcdfaba@google.com> <0000000000008c75b50583ddb5f8@google.com> <20190312040829.GQ2217@ZenIV.linux.org.uk> <491ff1c3-91d6-eaa7-f551-46a4f8b90f5a@i-love.sakura.ne.jp> <92a4e5e5-33ca-7b39-16c0-82c7fb742d18@i-love.sakura.ne.jp> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Mar 13, 2019 at 07:43:38AM +0100, Dmitry Vyukov wrote: > It would be more useful to accept patches that make syzkaller create > better reproducers from these people. Manual work is not scalable. We > would need 10 reproducers per day for a dozen of OSes (incl some > private kernels/branches). Anybody is free to run syzkaller manually > and do full manual (perfect) reporting. But for us it become clear > very early that it won't work. Then see above, while that human is > sleeping/on weekend/vacation, syzbot will already bisect own > reproducer. Adding manual reproducer later won't help in any way. > syzkaller already does lots of smart work for reproducers. Let's not > give up on the last mile and switch back to all manual work. I suspect a scalable solution that would significantly improve things is one where Syzbot tries N times for a "good" result to make sure it's not a flaky pass. N could either be hard-coded to some value like 8 or 10, or Syzbot could experimentally try to figure out how reliable the reproducer happens to be, and figure out what an ideal "N" value should be for a particular reproducer. - Ted