From: Thomas Gleixner <[email protected]>
When a serial port is used for kernel console output, then all
modifications to the UART registers which are done from other contexts,
e.g. getty, termios, are interference points for the kernel console.
So far this has been ignored and the printk output is based on the
principle of hope. The rework of the console infrastructure which aims to
support threaded and atomic consoles, requires to mark sections which
modify the UART registers as unsafe. This allows the atomic write function
to make informed decisions and eventually to restore operational state. It
also allows to prevent the regular UART code from modifying UART registers
while printk output is in progress.
All modifications of UART registers are guarded by the UART port lock,
which provides an obvious synchronization point with the console
infrastructure.
To avoid adding this functionality to all UART drivers, wrap the
spin_[un]lock*() invocations for uart_port::lock into helper functions
which just contain the spin_[un]lock*() invocations for now. In a
subsequent step these helpers will gain the console synchronization
mechanisms.
Converted with coccinelle. No functional change.
Signed-off-by: Thomas Gleixner <[email protected]>
---
drivers/tty/serial/digicolor-usart.c | 18 +++++++++---------
1 file changed, 9 insertions(+), 9 deletions(-)
diff --git a/drivers/tty/serial/digicolor-usart.c b/drivers/tty/serial/digicolor-usart.c
index 128b5479e813..5004125f3045 100644
--- a/drivers/tty/serial/digicolor-usart.c
+++ b/drivers/tty/serial/digicolor-usart.c
@@ -133,7 +133,7 @@ static void digicolor_uart_rx(struct uart_port *port)
{
unsigned long flags;
- spin_lock_irqsave(&port->lock, flags);
+ uart_port_lock_irqsave(port, &flags);
while (1) {
u8 status, ch, ch_flag;
@@ -172,7 +172,7 @@ static void digicolor_uart_rx(struct uart_port *port)
ch_flag);
}
- spin_unlock_irqrestore(&port->lock, flags);
+ uart_port_unlock_irqrestore(port, flags);
tty_flip_buffer_push(&port->state->port);
}
@@ -185,7 +185,7 @@ static void digicolor_uart_tx(struct uart_port *port)
if (digicolor_uart_tx_full(port))
return;
- spin_lock_irqsave(&port->lock, flags);
+ uart_port_lock_irqsave(port, &flags);
if (port->x_char) {
writeb_relaxed(port->x_char, port->membase + UA_EMI_REC);
@@ -211,7 +211,7 @@ static void digicolor_uart_tx(struct uart_port *port)
uart_write_wakeup(port);
out:
- spin_unlock_irqrestore(&port->lock, flags);
+ uart_port_unlock_irqrestore(port, flags);
}
static irqreturn_t digicolor_uart_int(int irq, void *dev_id)
@@ -333,7 +333,7 @@ static void digicolor_uart_set_termios(struct uart_port *port,
port->ignore_status_mask |= UA_STATUS_OVERRUN_ERR
| UA_STATUS_PARITY_ERR | UA_STATUS_FRAME_ERR;
- spin_lock_irqsave(&port->lock, flags);
+ uart_port_lock_irqsave(port, &flags);
uart_update_timeout(port, termios->c_cflag, baud);
@@ -341,7 +341,7 @@ static void digicolor_uart_set_termios(struct uart_port *port,
writeb_relaxed(divisor & 0xff, port->membase + UA_HBAUD_LO);
writeb_relaxed(divisor >> 8, port->membase + UA_HBAUD_HI);
- spin_unlock_irqrestore(&port->lock, flags);
+ uart_port_unlock_irqrestore(port, flags);
}
static const char *digicolor_uart_type(struct uart_port *port)
@@ -398,14 +398,14 @@ static void digicolor_uart_console_write(struct console *co, const char *c,
int locked = 1;
if (oops_in_progress)
- locked = spin_trylock_irqsave(&port->lock, flags);
+ locked = uart_port_trylock_irqsave(port, &flags);
else
- spin_lock_irqsave(&port->lock, flags);
+ uart_port_lock_irqsave(port, &flags);
uart_console_write(port, c, n, digicolor_uart_console_putchar);
if (locked)
- spin_unlock_irqrestore(&port->lock, flags);
+ uart_port_unlock_irqrestore(port, flags);
/* Wait for transmitter to become empty */
do {
--
2.39.2
Hi John,
On Thu, Sep 14 2023, John Ogness wrote:
> From: Thomas Gleixner <[email protected]>
>
> When a serial port is used for kernel console output, then all
> modifications to the UART registers which are done from other contexts,
> e.g. getty, termios, are interference points for the kernel console.
>
> So far this has been ignored and the printk output is based on the
> principle of hope. The rework of the console infrastructure which aims to
> support threaded and atomic consoles, requires to mark sections which
> modify the UART registers as unsafe. This allows the atomic write function
> to make informed decisions and eventually to restore operational state. It
> also allows to prevent the regular UART code from modifying UART registers
> while printk output is in progress.
>
> All modifications of UART registers are guarded by the UART port lock,
> which provides an obvious synchronization point with the console
> infrastructure.
>
> To avoid adding this functionality to all UART drivers, wrap the
> spin_[un]lock*() invocations for uart_port::lock into helper functions
> which just contain the spin_[un]lock*() invocations for now. In a
> subsequent step these helpers will gain the console synchronization
> mechanisms.
>
> Converted with coccinelle. No functional change.
>
> Signed-off-by: Thomas Gleixner <[email protected]>
Acked-by: Baruch Siach <[email protected]>
Thanks,
baruch
> ---
> drivers/tty/serial/digicolor-usart.c | 18 +++++++++---------
> 1 file changed, 9 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/tty/serial/digicolor-usart.c b/drivers/tty/serial/digicolor-usart.c
> index 128b5479e813..5004125f3045 100644
> --- a/drivers/tty/serial/digicolor-usart.c
> +++ b/drivers/tty/serial/digicolor-usart.c
> @@ -133,7 +133,7 @@ static void digicolor_uart_rx(struct uart_port *port)
> {
> unsigned long flags;
>
> - spin_lock_irqsave(&port->lock, flags);
> + uart_port_lock_irqsave(port, &flags);
>
> while (1) {
> u8 status, ch, ch_flag;
> @@ -172,7 +172,7 @@ static void digicolor_uart_rx(struct uart_port *port)
> ch_flag);
> }
>
> - spin_unlock_irqrestore(&port->lock, flags);
> + uart_port_unlock_irqrestore(port, flags);
>
> tty_flip_buffer_push(&port->state->port);
> }
> @@ -185,7 +185,7 @@ static void digicolor_uart_tx(struct uart_port *port)
> if (digicolor_uart_tx_full(port))
> return;
>
> - spin_lock_irqsave(&port->lock, flags);
> + uart_port_lock_irqsave(port, &flags);
>
> if (port->x_char) {
> writeb_relaxed(port->x_char, port->membase + UA_EMI_REC);
> @@ -211,7 +211,7 @@ static void digicolor_uart_tx(struct uart_port *port)
> uart_write_wakeup(port);
>
> out:
> - spin_unlock_irqrestore(&port->lock, flags);
> + uart_port_unlock_irqrestore(port, flags);
> }
>
> static irqreturn_t digicolor_uart_int(int irq, void *dev_id)
> @@ -333,7 +333,7 @@ static void digicolor_uart_set_termios(struct uart_port *port,
> port->ignore_status_mask |= UA_STATUS_OVERRUN_ERR
> | UA_STATUS_PARITY_ERR | UA_STATUS_FRAME_ERR;
>
> - spin_lock_irqsave(&port->lock, flags);
> + uart_port_lock_irqsave(port, &flags);
>
> uart_update_timeout(port, termios->c_cflag, baud);
>
> @@ -341,7 +341,7 @@ static void digicolor_uart_set_termios(struct uart_port *port,
> writeb_relaxed(divisor & 0xff, port->membase + UA_HBAUD_LO);
> writeb_relaxed(divisor >> 8, port->membase + UA_HBAUD_HI);
>
> - spin_unlock_irqrestore(&port->lock, flags);
> + uart_port_unlock_irqrestore(port, flags);
> }
>
> static const char *digicolor_uart_type(struct uart_port *port)
> @@ -398,14 +398,14 @@ static void digicolor_uart_console_write(struct console *co, const char *c,
> int locked = 1;
>
> if (oops_in_progress)
> - locked = spin_trylock_irqsave(&port->lock, flags);
> + locked = uart_port_trylock_irqsave(port, &flags);
> else
> - spin_lock_irqsave(&port->lock, flags);
> + uart_port_lock_irqsave(port, &flags);
>
> uart_console_write(port, c, n, digicolor_uart_console_putchar);
>
> if (locked)
> - spin_unlock_irqrestore(&port->lock, flags);
> + uart_port_unlock_irqrestore(port, flags);
>
> /* Wait for transmitter to become empty */
> do {
--
~. .~ Tk Open Systems
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