serial: bcm63xx: Use uart_prepare_sysrq_char().

The port lock is a spinlock_t which is becomes a sleeping lock on PREEMPT_RT.
The driver splits the locking function into two parts: local_irq_save() and
uart_port_lock() and this breaks PREEMPT_RT.

Delay handling sysrq until port lock is dropped.
Remove the special case in the console write routine an always use the
complete locking function.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Link: https://lore.kernel.org/r/20240301215246.891055-4-bigeasy@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/bcm63xx_uart.c b/drivers/tty/serial/bcm63xx_uart.c
index a3cefa153456df4a4d486b3784a03b99e1a4fc6e..34801a6f300b6841464f5195f9399ebd90b654d1 100644 (file)
--- a/drivers/tty/serial/bcm63xx_uart.c
+++ b/drivers/tty/serial/bcm63xx_uart.c
@@ -285,10 +285,9 @@ static void bcm_uart_do_rx(struct uart_port *port)
                                flag = TTY_PARITY;
                }
 
-               if (uart_handle_sysrq_char(port, c))
+               if (uart_prepare_sysrq_char(port, c))
                        continue;
 
-
                if ((cstat & port->ignore_status_mask) == 0)
                        tty_insert_flip_char(tty_port, c, flag);
 
@@ -353,7 +352,7 @@ static irqreturn_t bcm_uart_interrupt(int irq, void *dev_id)
                                               estat & UART_EXTINP_DCD_MASK);
        }
 
-       uart_port_unlock(port);
+       uart_unlock_and_check_sysrq(port);
        return IRQ_HANDLED;
 }
 
@@ -703,20 +702,14 @@ static void bcm_console_write(struct console *co, const char *s,
 {
        struct uart_port *port;
        unsigned long flags;
-       int locked;
+       int locked = 1;
 
        port = &ports[co->index];
 
-       local_irq_save(flags);
-       if (port->sysrq) {
-               /* bcm_uart_interrupt() already took the lock */
-               locked = 0;
-       } else if (oops_in_progress) {
-               locked = uart_port_trylock(port);
-       } else {
-               uart_port_lock(port);
-               locked = 1;
-       }
+       if (oops_in_progress)
+               locked = uart_port_trylock_irqsave(port, &flags);
+       else
+               uart_port_lock_irqsave(port, &flags);
 
        /* call helper to deal with \r\n */
        uart_console_write(port, s, count, bcm_console_putchar);
@@ -725,8 +718,7 @@ static void bcm_console_write(struct console *co, const char *s,
        wait_for_xmitr(port);
 
        if (locked)
-               uart_port_unlock(port);
-       local_irq_restore(flags);
+               uart_port_unlock_irqrestore(port, flags);
 }
 
 /*