linux-kernel - Re: [PATCH] tty/serial: Cancel work queue before closing uart

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Message-ID: <CAB9BWhct+pO4a6i0BE6Zt3zhyjZQr1Dv14ZozssMc4edAWwgWw@mail.gmail.com>
Date:   Thu, 24 Aug 2023 10:36:11 +0800
From:   wenhua lin <wenhua.lin1994@...il.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Wenhua Lin <Wenhua.Lin@...soc.com>,
        Orson Zhai <orsonzhai@...il.com>,
        Baolin Wang <baolin.wang@...ux.alibaba.com>,
        Chunyan Zhang <zhang.lyra@...il.com>,
        linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org,
        Xiongpeng Wu <xiongpeng.wu@...soc.com>,
        Zhirong Qiu <zhirong.qiu@...soc.com>,
        Zhaochen Su <Zhaochen.Su@...soc.com>
Subject: Re: [PATCH] tty/serial: Cancel work queue before closing uart

On Tue, Aug 22, 2023 at 9:27 PM Greg Kroah-Hartman
<gregkh@...uxfoundation.org> wrote:
>
> On Fri, Aug 18, 2023 at 11:15:32AM +0800, Wenhua Lin wrote:
> > When the system constantly sleeps and wankes up, plugging and unplugging
> > the USB will probalility trigger a kernel crash problem. The reason is
> > that at this time, the system entered deep and turned off uart, and the
> > abnormal behavior of plugging and upplugging the USB triggered the read
> > data process of uart, causing access to uart to hang. The final solution
> > we came up with is to cancel the work queue before shutting down uart
> > , while ensuring that there is no uart business.
> >
> > Signed-off-by: Wenhua Lin <Wenhua.Lin@...soc.com>
> > ---
> >  drivers/tty/serial/sprd_serial.c | 4 ++++
> >  1 file changed, 4 insertions(+)
> >
> > diff --git a/drivers/tty/serial/sprd_serial.c b/drivers/tty/serial/sprd_serial.c
> > index b58f51296ace..eddff4360155 100644
> > --- a/drivers/tty/serial/sprd_serial.c
> > +++ b/drivers/tty/serial/sprd_serial.c
> > @@ -20,6 +20,7 @@
> >  #include <linux/slab.h>
> >  #include <linux/tty.h>
> >  #include <linux/tty_flip.h>
> > +#include "../tty.h"
> >
> >  /* device name */
> >  #define UART_NR_MAX          8
> > @@ -1221,7 +1222,10 @@ static int sprd_probe(struct platform_device *pdev)
> >  static int sprd_suspend(struct device *dev)
> >  {
> >       struct sprd_uart_port *sup = dev_get_drvdata(dev);
> > +     struct uart_port *uport = &sup->port;
> > +     struct tty_port *tty = &uport->state->port;
> >
> > +     tty_buffer_cancel_work(tty);
>
> What does this serial port have to do with the USB subsystem in your
> changelog text?
>
> And as the kernel bot said, this breaks the build, you can't do this
> within a serial driver, sorry.

This modification is not directly related to the usb subsystem.
I just described a problem scenario, such as the previous comment.
There may be problems with this solution. I will make changes on patch v2,
thank you for your review

>
> greg k-h