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: <CA+G9fYt49jY+sAqHXYwpJtF0oa-jL8t8nArY6W1_zui0sKFipA@mail.gmail.com>
 <29824864-f076-401f-bfb4-bc105bb2d38f@app.fastmail.com> <96a99291-7caa-429c-9bbd-29721a2b5637@app.fastmail.com>
In-Reply-To: <96a99291-7caa-429c-9bbd-29721a2b5637@app.fastmail.com>
From:   Dmitry Torokhov <dmitry.torokhov@gmail.com>
Date:   Thu, 10 Nov 2022 16:48:01 -0800
Message-ID: <CAKdAkRTOanSFKzmDgJc9oi1CM9D5D97+_oz31-MM0ADOtY6A4Q@mail.gmail.com>
Subject: Re: arm: TI BeagleBoard X15 : Unable to handle kernel NULL pointer
 dereference at virtual address 00000369 - Internal error: Oops: 5 [#1] SMP ARM
To:     Arnd Bergmann <arnd@arndb.de>
Cc:     Naresh Kamboju <naresh.kamboju@linaro.org>,
        linux-stable <stable@vger.kernel.org>,
        open list <linux-kernel@vger.kernel.org>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        lkft-triage@lists.linaro.org,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Sasha Levin <sashal@kernel.org>,
        Linus Walleij <linus.walleij@linaro.org>,
        Mark Brown <broonie@kernel.org>,
        Liam Girdwood <lgirdwood@gmail.com>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

On Wed, Nov 9, 2022 at 2:20 PM Arnd Bergmann <arnd@arndb.de> wrote:
>
> On Wed, Nov 9, 2022, at 13:57, Arnd Bergmann wrote:
> >
> > One thing that sticks out is the print_constraints_debug() function
> > in the regulator framework, which uses a larger-than-average stack
> > to hold a string buffer, and then calls into the low-level
> > driver to get the actual data (regulator_get_voltage_rdev,
> > _regulator_is_enabled). Splitting the device access out into a
> > different function from the string handling might reduce the
> > stack usage enough to stay just under the 8KB limit, though it's
> > probably not a complete fix. I added the regulator maintainers
> > to Cc for thoughts on this.
>
> I checked the stack usage for each of the 147 functions in the
> backtrace, and as I was guessing print_constraints_debug() is
> the largest, but it's still only 168 bytes, and everything else
> is smaller, so no point hacking this.

You mentioned that we are doing probing of a device 6 levels deep.
Could one of the parent devices be marked for an asynchronous probe
thus breaking the chain?

Thanks.

-- 
Dmitry