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SubjectRe: [PATCH 3/3] serial: stm32: defer sysrq processing
Date
Hi,

On 4/16/21 4:05 PM, Johan Hovold wrote:
> Use the uart_unlock_and_check_sysrq() helper to defer sysrq processing
> until receive processing is done and the port lock has been released.
>
> This allows cleaning up the console_write() implementation by not having
> to work around the recursive sysrq case (by dropping locking completely)
> and also makes the console code work with PREEMPT_RT by no longer
> relying on local_irq_save().
>
> Signed-off-by: Johan Hovold <johan@kernel.org>

Reviewed-by: Valentin Caron<valentin.caron@foss.st.com>

> ---
> drivers/tty/serial/stm32-usart.c | 16 ++++++----------
> 1 file changed, 6 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c
> index 3524ed2c0c73..24a1dfe7058b 100644
> --- a/drivers/tty/serial/stm32-usart.c
> +++ b/drivers/tty/serial/stm32-usart.c
> @@ -270,12 +270,12 @@ static void stm32_usart_receive_chars(struct uart_port *port, bool threaded)
> }
> }
>
> - if (uart_handle_sysrq_char(port, c))
> + if (uart_prepare_sysrq_char(port, c))
> continue;
> uart_insert_char(port, sr, USART_SR_ORE, c, flag);
> }
>
> - spin_unlock(&port->lock);
> + uart_unlock_and_check_sysrq(port);
>
> tty_flip_buffer_push(tport);
> }
> @@ -1430,13 +1430,10 @@ static void stm32_usart_console_write(struct console *co, const char *s,
> u32 old_cr1, new_cr1;
> int locked = 1;
>
> - local_irq_save(flags);
> - if (port->sysrq)
> - locked = 0;
> - else if (oops_in_progress)
> - locked = spin_trylock(&port->lock);
> + if (oops_in_progress)
> + locked = spin_trylock_irqsave(&port->lock, flags);
> else
> - spin_lock(&port->lock);
> + spin_lock_irqsave(&port->lock, flags);
>
> /* Save and disable interrupts, enable the transmitter */
> old_cr1 = readl_relaxed(port->membase + ofs->cr1);
> @@ -1450,8 +1447,7 @@ static void stm32_usart_console_write(struct console *co, const char *s,
> writel_relaxed(old_cr1, port->membase + ofs->cr1);
>
> if (locked)
> - spin_unlock(&port->lock);
> - local_irq_restore(flags);
> + spin_unlock_irqrestore(&port->lock, flags);
> }
>
> static int stm32_usart_console_setup(struct console *co, char *options)
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