From: Jonathan Liu <net147@gmail.com>
To: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Cc: Will Deacon <will@kernel.org>,
Hans de Goede <hdegoede@redhat.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
linux-kernel <linux-kernel@vger.kernel.org>,
Maxime Ripard <mripard@kernel.org>,
Russell King <linux@armlinux.org.uk>,
Alexey Malahov <Alexey.Malahov@baikalelectronics.ru>,
Andy Shevchenko <andy.shevchenko@gmail.com>,
Serge Semin <fancer.lancer@gmail.com>,
linux-serial@vger.kernel.org,
Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
Jiri Slaby <jirislaby@kernel.org>,
linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
Pavel Parkhomenko <Pavel.Parkhomenko@baikalelectronics.ru>
Subject: Re: [PATCH 3/3] serial: 8250_dw: Fix clk-notifier/port suspend deadlock
Date: Sun, 18 Oct 2020 11:32:06 +1100 [thread overview]
Message-ID: <CANwerB2GzDiM__UzzfHRn9ENvXYVabRZq8J9ArHcDmWT9zEKNA@mail.gmail.com> (raw)
In-Reply-To: <20200923161950.6237-4-Sergey.Semin@baikalelectronics.ru>
On Wed, 23 Sep 2020 at 16:19, Serge Semin
<Sergey.Semin@baikalelectronics.ru> wrote:
>
> It has been discovered that there is a potential deadlock between
> the clock-change-notifier thread and the UART port suspending one:
>
> CPU0 (suspend CPU/UART) CPU1 (update clock)
> ---- ----
> lock(&port->mutex);
> lock((work_completion)(&data->clk_work));
> lock(&port->mutex);
> lock((work_completion)(&data->clk_work));
>
> *** DEADLOCK ***
>
> The best way to fix this is to eliminate the CPU0
> port->mutex/work-completion scenario. So we suggest to register and
> unregister the clock-notifier during the DW APB UART port probe/remove
> procedures, instead of doing that at the points of the port
> startup/shutdown.
>
> Link: https://lore.kernel.org/linux-serial/f1cd5c75-9cda-6896-a4e2-42c5bfc3f5c3@redhat.com
>
> Fixes: cc816969d7b5 ("serial: 8250_dw: Fix common clocks usage race condition")
> Reported-by: Hans de Goede <hdegoede@redhat.com>
> Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Tested-by: Jonathan Liu <net147@gmail.com>
Fixes hang while closing the serial port on RK3399 that I was
experiencing often with Linux 5.9.
After applying this patch, it no longer hangs while closing the serial port.
No problems while rebooting either.
Thanks.
Regards,
Jonathan
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next prev parent reply other threads:[~2020-10-18 0:34 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-23 16:19 [PATCH 0/3] serial: 8250_dw: Fix clk-notifier/port suspend deadlock Serge Semin
2020-09-23 16:19 ` [PATCH 1/3] serial: 8250: Discard RTS/DTS setting from clock update method Serge Semin
2020-09-23 16:19 ` [PATCH 2/3] serial: 8250: Skip uninitialized TTY port baud rate update Serge Semin
2020-09-23 16:19 ` [PATCH 3/3] serial: 8250_dw: Fix clk-notifier/port suspend deadlock Serge Semin
2020-10-18 0:32 ` Jonathan Liu [this message]
2020-09-27 15:01 ` [PATCH 0/3] " Hans de Goede
2020-09-29 20:51 ` Serge Semin
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