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=-13.4 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_IN_DEF_DKIM_WL 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 4ED58C49ED7 for ; Mon, 16 Sep 2019 15:29:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1E3AC206A4 for ; Mon, 16 Sep 2019 15:29:52 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="r4xQx2sZ" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389147AbfIPP3v (ORCPT ); Mon, 16 Sep 2019 11:29:51 -0400 Received: from mail-pg1-f194.google.com ([209.85.215.194]:34716 "EHLO mail-pg1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727374AbfIPP3v (ORCPT ); Mon, 16 Sep 2019 11:29:51 -0400 Received: by mail-pg1-f194.google.com with SMTP id n9so218192pgc.1 for ; Mon, 16 Sep 2019 08:29:50 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=+y4AkvsKSUe07hNkypQ1HfKQPXtAqApgQQ2c6pYsyvM=; b=r4xQx2sZTsVMGJQTG+yP4K5+89JMjruqVFAgOZPhHjy/5EkjLo1a+GA6OjtG8UcSAO fvBhCoNTRyRrS6Ofwjw+bvMrNKaGQkXc1Uuk9sFidnQFMWlNE0jPWFEhejNhE6IvaJDA m8mYa79vRNAwdeqXH6tiYsmBklPEU+vPM4OCoAjyp7c701HPMbeM0QF1B66YfF2EoD9T jI7RZ2FLOTYh61RKVmjkGCq1L0resvYIZdl0COVppwxBXUik4hh127syb1lEODBawtYR qyXRY5d02OFbdtt7s3xfzuwme6NwGVVbYTa7Q3Z9JbUNYkHgmsdHlsyLIRnbvKyrewHR kZig== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=+y4AkvsKSUe07hNkypQ1HfKQPXtAqApgQQ2c6pYsyvM=; b=eQ7acYTrEP6xruAJBgkVhnp4jzXqYnO9tvqVuuUm+i03GnuhWGCSIpYv2ssiYJn/Yf VFbLqb1GMK/KM5/5OWHCWPwWecBtLhigm1pBzR0bqS3U2Iz5NPvP855rTmJdQe0+XyCb c1AEz5qXuvgC57UTDBiixt5XmavGp1F25hQOTvO4CeYg/L3Ybt1dH8KlUfxc7/4IEK+k Pr/CO+DJUJCiG5wfKhT+PCQy2x5i2BVDRWq/Yx785KovYBlZxLw7spohIy3fSpIqj1mQ 0FsqI0syf7NNJfL4lZ9ssp/YG4obkGRgXC6GG/wucLad13h3lO9Pxva6ZUTW3dTMfu62 TLDA== X-Gm-Message-State: APjAAAXQcDYbgVy0VlToNqgocYNR+ryJ2gxI1srGP6QUQImy9coPSuPi pvaqjRpRP2onopYS5+yw1a5XaIiGENPVt112NP4xFg== X-Google-Smtp-Source: APXvYqx/vQc7AckoJDceJnazN6xeds3moRiKMgeAsWhEzJVlkiGKHFbOefeJamw6iyqI1oA7OyuAW3Aoh1iFTqCs1mE= X-Received: by 2002:a17:90a:1990:: with SMTP id 16mr278460pji.47.1568647790078; Mon, 16 Sep 2019 08:29:50 -0700 (PDT) MIME-Version: 1.0 References: <0000000000004fb020059274a5ff@google.com> In-Reply-To: From: Andrey Konovalov Date: Mon, 16 Sep 2019 17:29:39 +0200 Message-ID: Subject: Re: INFO: rcu detected stall in dummy_timer To: Alan Stern Cc: syzbot , Felipe Balbi , chunfeng.yun@mediatek.com, Greg Kroah-Hartman , LKML , USB list , syzkaller-bugs , Dmitry Vyukov Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Sep 13, 2019 at 10:35 PM Alan Stern wrote: > > On Fri, 13 Sep 2019, syzbot wrote: > > > syzbot has found a reproducer for the following crash on: > > > > HEAD commit: f0df5c1b usb-fuzzer: main usb gadget fuzzer driver > > git tree: https://github.com/google/kasan.git usb-fuzzer > > console output: https://syzkaller.appspot.com/x/log.txt?x=1146550d600000 > > kernel config: https://syzkaller.appspot.com/x/.config?x=5c6633fa4ed00be5 > > dashboard link: https://syzkaller.appspot.com/bug?extid=b24d736f18a1541ad550 > > compiler: gcc (GCC) 9.0.0 20181231 (experimental) > > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=11203fa5600000 > > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=162cd335600000 > > > > IMPORTANT: if you fix the bug, please add the following tag to the commit: > > Reported-by: syzbot+b24d736f18a1541ad550@syzkaller.appspotmail.com > > > > yurex 3-1:0.101: yurex_interrupt - unknown status received: -71 > > yurex 5-1:0.101: yurex_interrupt - unknown status received: -71 > > yurex 6-1:0.101: yurex_interrupt - unknown status received: -71 > > rcu: INFO: rcu_sched self-detected stall on CPU > > Andrey: > > This problem may be a result of overloading dummy_timer. The kernel > config you are using has CONFIG_HZ=100, but dummy-hcd needs > CONFIG_HZ=1000 (see the comment on line 1789). That is, lower values > of HZ will occasionally lead to trouble, and this may be an example. > > Can you change the config value for HZ and see if the bug still > reproduces? Hi Alan, I've tried running the reproducer with CONFIG_HZ=1000 and still got the same stall message. It's accompanied by countless "yurex 6-1:0.101: yurex_interrupt - unknown status received: -71" messages, so I believe this is an issue in the yurex driver. Why does dumy_hcd require CONFIG_HZ=1000? The comment doesn't really explain the reason. Thanks!