Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
MIME-Version: 1.0
References: <20220619204949.50d9154d@thinkpad> <YrAEUM20n3Rc4aOn@google.com>
 <20220620120234.5a65ac97@thinkpad> <YrBIURn7lxykWghw@google.com> <20220620122904.30c06c4e@thinkpad>
In-Reply-To: <20220620122904.30c06c4e@thinkpad>
From:   Andy Shevchenko <andy.shevchenko@gmail.com>
Date:   Mon, 20 Jun 2022 13:01:28 +0200
Message-ID: <CAHp75VdcY1TAksJ10gFPJbagVVfYoe08J9c3Ow_X7dGRrrNyyQ@mail.gmail.com>
Subject: Re: Boot stall regression from "printk for 5.19" merge
To:     =?UTF-8?B?TWFyZWsgQmVow7pu?= <kabel@kernel.org>,
        =?UTF-8?Q?Ilpo_J=C3=A4rvinen?= <ilpo.jarvinen@linux.intel.com>
Cc:     Sergey Senozhatsky <senozhatsky@chromium.org>,
        John Ogness <john.ogness@linutronix.de>,
        Petr Mladek <pmladek@suse.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
Precedence: bulk

+Cc: Ilpo, a new maintainer for the driver

On Mon, Jun 20, 2022 at 12:46 PM Marek Beh=C3=BAn <kabel@kernel.org> wrote:
>
> On Mon, 20 Jun 2022 19:13:37 +0900
> Sergey Senozhatsky <senozhatsky@chromium.org> wrote:
>
> > On (22/06/20 12:02), Marek Beh=C3=BAn wrote:
> > > > On (22/06/19 20:49), Marek Beh=C3=BAn wrote:
> > > > [..]
> > > > > causes a regression on arm64 (Marvell CN9130-CRB board) where the
> > > > > system boot freezes in most cases (and is unusable until restarte=
d by
> > > > > watchdog), or, in some cases boots, but the console output gets m=
angled
> > > > > for a while (the serial console spits garbage characters).
> > > >
> > > > Can you please try disabling console kthreads and see how the boot
> > > > process goes? Just `return 0` from printk_activate_kthreads() (I th=
ink
> > > > this should do the trick).
> > >
> > > This indeed makes the problem go away...
> >
> > Oh... OK. Didn't expect that :)
> >
> > > > > The garbage example:
> > > > >
> > > > >   ...
> > > > >   [    0.920951] raid6: using neon recovery algorithm
> > > > >   [    0.921228] iommu: Default domain type: Translated
> > > > >   %
> > > > >
> > > > >           gb@k+cFL/[    4.954974] DSA: tree 0 setup
> > > > >   [    4.955286] cfg80211: Loading compiled-in X.509 certificates=
 for regulatory database
> > > >
> > > > This is pretty suspicious. I don't see how console kthreads would
> > > > corrupt the output. I suspect that something else is going on, some
> > > > memory corruption, etc.
> > >
> > > Maybe multiple threads are writing to serial registers, or something.=
..
> >
> > That's possible. Console drivers usually should grab port->lock for
> > write(), but maybe something is missing in the driver you use. What
> > console driver are you using?
>
> compatible =3D "snps,dw-apb-uart", so drivers/tty/serial/8250/8250_dw.c
>
> seems that the function dw8250_serial_out() does not use the spinlock...
>
> Marek


--=20
With Best Regards,
Andy Shevchenko