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=-6.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable 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 CA6ECC4CEC5 for ; Fri, 13 Sep 2019 20:36:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A54F4206A4 for ; Fri, 13 Sep 2019 20:36:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730835AbfIMUf7 (ORCPT ); Fri, 13 Sep 2019 16:35:59 -0400 Received: from iolanthe.rowland.org ([192.131.102.54]:54316 "HELO iolanthe.rowland.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1730023AbfIMUf6 (ORCPT ); Fri, 13 Sep 2019 16:35:58 -0400 Received: (qmail 6179 invoked by uid 2102); 13 Sep 2019 16:35:57 -0400 Received: from localhost (sendmail-bs@127.0.0.1) by localhost with SMTP; 13 Sep 2019 16:35:57 -0400 Date: Fri, 13 Sep 2019 16:35:57 -0400 (EDT) From: Alan Stern X-X-Sender: stern@iolanthe.rowland.org To: syzbot cc: andreyknvl@google.com, , , , , , Subject: Re: INFO: rcu detected stall in dummy_timer In-Reply-To: <0000000000004fb020059274a5ff@google.com> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-usb-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org 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? Alan Stern