linux-kernel - Re: [PATCH 02/18] serial: sc16is7xx: fix invalid sc16is7xx

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Date: Thu, 21 Dec 2023 18:16:40 +0200
From: Andy Shevchenko <andriy.shevchenko@...el.com>
To: Hugo Villeneuve <hugo@...ovil.com>
Cc: gregkh@...uxfoundation.org, jirislaby@...nel.org, jringle@...dpoint.com,
	kubakici@...pl, phil@...pberrypi.org, bo.svangard@...eddedart.se,
	linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org,
	Hugo Villeneuve <hvilleneuve@...onoff.com>, stable@...r.kernel.org,
	Yury Norov <yury.norov@...il.com>
Subject: Re: [PATCH 02/18] serial: sc16is7xx: fix invalid sc16is7xx_lines
 bitfield in case of probe error

On Thu, Dec 21, 2023 at 11:13:37AM -0500, Hugo Villeneuve wrote:
> On Thu, 21 Dec 2023 10:56:39 -0500
> Hugo Villeneuve <hugo@...ovil.com> wrote:
> > On Wed, 20 Dec 2023 17:40:42 +0200
> > Andy Shevchenko <andriy.shevchenko@...el.com> wrote:

...

> > this will indeed fix the problem described in patch 1.
> > 
> > However, if I remove patch 1, and I simulate the same probe error as
> > described in patch 1, now we get stuck forever when trying to 
> > remove the driver. This is something that I observed before and
> > that patch 1 also corrected.
> > 
> > The problem is caused in sc16is7xx_remove() when calling this function
> > 
> >     kthread_flush_worker(&s->kworker);
> > 
> > I am not sure how best to handle that without patch 1.
> 
> Also, if we manage to get past kthread_flush_worker() and 
> kthread_stop() (commented out for testing purposes), we get another bug:
> 
> # rmmod sc16is7xx
> ...
> crystal-duart-24m already disabled
> WARNING: CPU: 2 PID: 340 at drivers/clk/clk.c:1090
> clk_core_disable+0x1b0/0x1e0
> ...
> Call trace:
> clk_core_disable+0x1b0/0x1e0
> clk_disable+0x38/0x60
> sc16is7xx_remove+0x1e4/0x240 [sc16is7xx]
> 
> This one is caused by calling clk_disable_unprepare(). But
> clk_disable_unprepare() has already been called in probe error handling
> code. Patch 1 also fixed this...

Word "fixed" is incorrect. "Papered over" is what it did.

-- 
With Best Regards,
Andy Shevchenko