Linux-USB Archive on lore.kernel.org
 help / color / Atom feed
From: Andrey Konovalov <andreyknvl@google.com>
To: Alan Stern <stern@rowland.harvard.edu>
Cc: syzbot <syzbot+b24d736f18a1541ad550@syzkaller.appspotmail.com>,
	Felipe Balbi <balbi@kernel.org>,
	chunfeng.yun@mediatek.com,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	LKML <linux-kernel@vger.kernel.org>,
	USB list <linux-usb@vger.kernel.org>,
	syzkaller-bugs <syzkaller-bugs@googlegroups.com>,
	Dmitry Vyukov <dvyukov@google.com>
Subject: Re: INFO: rcu detected stall in dummy_timer
Date: Mon, 16 Sep 2019 17:29:39 +0200
Message-ID: <CAAeHK+zrR3pB2R3yyyUdGM4Vrv77o47MHsgvbQ+LFHfiWBt1OQ@mail.gmail.com> (raw)
In-Reply-To: <Pine.LNX.4.44L0.1909131629230.1466-100000@iolanthe.rowland.org>

On Fri, Sep 13, 2019 at 10:35 PM Alan Stern <stern@rowland.harvard.edu> 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!

  reply index

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-09 13:18 syzbot
2019-09-13 19:56 ` syzbot
2019-09-13 20:35   ` Alan Stern
2019-09-16 15:29     ` Andrey Konovalov [this message]
2019-09-16 16:32       ` Alan Stern
2019-09-16 18:59         ` Greg Kroah-Hartman
2019-09-16 19:48           ` Alan Stern
2019-09-18 11:22         ` Andrey Konovalov
2019-09-18 14:16           ` Alan Stern
2019-09-16 19:53   ` Alan Stern
2019-09-16 20:13     ` syzbot
2019-09-17 16:47       ` [PATCH] USB: yurex: Don't retry on unexpected errors Alan Stern

Reply instructions:

You may reply publically to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=CAAeHK+zrR3pB2R3yyyUdGM4Vrv77o47MHsgvbQ+LFHfiWBt1OQ@mail.gmail.com \
    --to=andreyknvl@google.com \
    --cc=balbi@kernel.org \
    --cc=chunfeng.yun@mediatek.com \
    --cc=dvyukov@google.com \
    --cc=gregkh@linuxfoundation.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-usb@vger.kernel.org \
    --cc=stern@rowland.harvard.edu \
    --cc=syzbot+b24d736f18a1541ad550@syzkaller.appspotmail.com \
    --cc=syzkaller-bugs@googlegroups.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Linux-USB Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-usb/0 linux-usb/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-usb linux-usb/ https://lore.kernel.org/linux-usb \
		linux-usb@vger.kernel.org linux-usb@archiver.kernel.org
	public-inbox-index linux-usb

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-usb


AGPL code for this site: git clone https://public-inbox.org/ public-inbox