linux-kernel - Re: [PATCH] tty: serial: samsung_tty: remove spinlock flags in interrupt handlers

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Date:   Tue, 16 Mar 2021 11:40:57 +0200
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Johan Hovold <johan@...nel.org>,
        Finn Thain <fthain@...egraphics.com.au>,
        Barry Song <song.bao.hua@...ilicon.com>
Cc:     Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>,
        linux-arm Mailing List <linux-arm-kernel@...ts.infradead.org>,
        Linux Samsung SOC <linux-samsung-soc@...r.kernel.org>,
        "open list:SERIAL DRIVERS" <linux-serial@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Hector Martin <marcan@...can.st>,
        Arnd Bergmann <arnd@...nel.org>
Subject: Re: [PATCH] tty: serial: samsung_tty: remove spinlock flags in
 interrupt handlers

On Tue, Mar 16, 2021 at 11:02 AM Johan Hovold <johan@...nel.org> wrote:
>
> On Mon, Mar 15, 2021 at 07:12:12PM +0100, Krzysztof Kozlowski wrote:
> > Since interrupt handler is called with disabled local interrupts, there
> > is no need to use the spinlock primitives disabling interrupts as well.
>
> This isn't generally true due to "threadirqs" and that can lead to
> deadlocks if the console code is called from hard irq context.
>
> Now, this is *not* the case for this particular driver since it doesn't
> even bother to take the port lock in console_write(). That should
> probably be fixed instead.
>
> See https://lore.kernel.org/r/X7kviiRwuxvPxC8O@localhost.

Finn, Barry, something to check I think?

--
With Best Regards,
Andy Shevchenko