From: "Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>
To: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: kernel@pengutronix.de, linux-serial@vger.kernel.org
Subject: Re: NULL pointer dereference when closing a busy UART
Date: Tue, 16 Apr 2024 19:07:38 +0200 [thread overview]
Message-ID: <wmfb6m7gz5ym2exep4pgmtwqonxi5eqryif4herfkc5rbxxvre@eqnzhic3umux> (raw)
In-Reply-To: <Zh6Sb-Gk_RIdHkZi@smile.fi.intel.com>
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Hello Andy,
On Tue, Apr 16, 2024 at 05:59:59PM +0300, Andy Shevchenko wrote:
> On Tue, Apr 16, 2024 at 11:52:19AM +0200, Uwe Kleine-König wrote:
> > On Mon, Apr 15, 2024 at 10:04:39PM +0200, Uwe Kleine-König wrote:
> > > On Mon, Apr 15, 2024 at 10:36:44PM +0300, Andy Shevchenko wrote:
> > > > On Mon, Apr 15, 2024 at 07:15:54PM +0200, Uwe Kleine-König wrote:
>
> ...
>
> > > > You might need this
> > > >
> > > > 1aa4ad4eb695 serial: core: Fix missing shutdown and startup for serial base port
> > > >
> > > > on top btw.
> > >
> > > Ah, that looks exactly like my issue. Thanks, I will test that an report
> > > back.
> >
> > It improves my situation for sure. I have yet another problem with the
> > stm32 UART that is driver specfic. I'm working on that one now ...
>
> Please, Cc me on that when publishing, I'm curious.
I don't have a fix yet, but the problem reproduces as follows:
I have a bridge between TX and RX; and also between RTS and CTS; there
is no DMA involved. I send a big amount of data and so receive that all.
This puts pressure on the receiving line discipline and so ->throttle()
is called.
->throttle() sets stm32_port->throttled = true; which makes the ISR (=
stm32_usart_interrupt()) stop handle USART_SR_RXNE (= RXFIFO not empty).
So the ISR is called in a tight loop. Stuck irq detection doesn't step
in because the ISR returns IRQ_HANDLED unconditionally. (For the latter
I already have a prototype patch.)
It's unclear to me yet, what to do. Some further things that are (maybe)
relevant are:
- Without a rts-gpio the driver cannot toggle RTS. (Hardware
limitation)
- The driver makes no effort evaluating CTS.
Best regards
Uwe
--
Pengutronix e.K. | Uwe Kleine-König |
Industrial Linux Solutions | https://www.pengutronix.de/ |
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prev parent reply other threads:[~2024-04-16 17:07 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-15 17:15 NULL pointer dereference when closing a busy UART Uwe Kleine-König
2024-04-15 19:36 ` Andy Shevchenko
2024-04-15 20:04 ` Uwe Kleine-König
2024-04-16 9:52 ` Uwe Kleine-König
2024-04-16 14:59 ` Andy Shevchenko
2024-04-16 17:07 ` Uwe Kleine-König [this message]
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