Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Sat, 23 Jan 2021 15:37:30 -0800 (PST)
From:   Hugh Dickins <hughd@google.com>
To:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "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>,
        Saravana Kannan <saravanak@google.com>,
        linux-pm@vger.kernel.org
Subject: Re: Infinite recursion in device_reorder_to_tail() due to circular
 device links
In-Reply-To: <X/3kveeVrb35qsvb@kroah.com>
Message-ID: <alpine.LSU.2.11.2101231524290.1540@eggly.anvils>
References: <X/ycQpu7NIGI969v@gerhold.net> <CAJZ5v0gAsZ45O8mv-gz0UvbyxnKA6fQBYvambBYEH6OSk3-m3g@mail.gmail.com> <X/3kveeVrb35qsvb@kroah.com>
User-Agent: Alpine 2.11 (LSU 23 2013-08-11)
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII
Precedence: bulk

On Tue, 12 Jan 2021, Greg Kroah-Hartman wrote:
> 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

I think that there has been a misunderstanding here: although
5b6164d3465f ("driver core: Reorder devices on successful probe")
has been reverted from linux-next (thank you), it has not yet been
reverted from 5.11-rc, and still causing problems there (in my case,
not the infinite recursion Stephan reported in this thread, but the
ThinkPad rmi4 suspend failure that I reported in another thread).

Thanks,
Hugh