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Date:   Tue, 12 Jan 2021 19:04:45 +0100
From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     "Rafael J. Wysocki" <rafael@kernel.org>
Cc:     Stephan Gerhold <stephan@gerhold.net>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Peter Chen <Peter.Chen@nxp.com>,
        Kishon Vijay Abraham I <kishon@ti.com>,
        "open list:ULTRA-WIDEBAND (UWB) SUBSYSTEM:" 
        <linux-usb@vger.kernel.org>, Thierry Reding <treding@nvidia.com>
Subject: Re: Infinite recursion in device_reorder_to_tail() due to circular
 device links
Message-ID: <X/3kveeVrb35qsvb@kroah.com>
References: <X/ycQpu7NIGI969v@gerhold.net>
 <CAJZ5v0gAsZ45O8mv-gz0UvbyxnKA6fQBYvambBYEH6OSk3-m3g@mail.gmail.com>
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On Tue, Jan 12, 2021 at 03:32:04PM +0100, Rafael J. Wysocki wrote:
> On Mon, Jan 11, 2021 at 7:46 PM Stephan Gerhold <stephan@gerhold.net> wrote:
> >
> > Hi,
> >
> > since 5.11-rc1 I get kernel crashes with infinite recursion in
> > device_reorder_to_tail() in some situations... It's a bit complicated to
> > explain so I want to apologize in advance for the long mail. :)
> >
> >   Kernel panic - not syncing: kernel stack overflow
> >   CPU: 1 PID: 33 Comm: kworker/1:1 Not tainted 5.11.0-rc3 #1
> >   Hardware name: Qualcomm Technologies, Inc. APQ 8016 SBC (DT)
> >   Call trace:
> >    ...
> >    device_reorder_to_tail+0x4c/0xf0
> >    device_reorder_to_tail+0x98/0xf0
> >    device_reorder_to_tail+0x60/0xf0
> >    device_reorder_to_tail+0x60/0xf0
> >    device_reorder_to_tail+0x60/0xf0
> >    ...
> >
> > The crash happens only in 5.11 with commit 5b6164d3465f ("driver core:
> > Reorder devices on successful probe"). It stops happening when I revert
> > this commit.
> 
> Thanks for the report!
> 
> Greg, please revert commit 5b6164d3465f, it clearly is not an
> improvement, at least at this point.

Now reverted, thanks.

greg k-h