serial: pch: 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/20240301215246.891055-19-bigeasy@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/pch_uart.c b/drivers/tty/serial/pch_uart.c
index 92cb3c623cc311c9d49e341143d80c285c6e38f9..89257cddf540503d3d41a3d2de74f35e81486192 100644 (file)
--- a/drivers/tty/serial/pch_uart.c
+++ b/drivers/tty/serial/pch_uart.c
@@ -564,7 +564,7 @@ static int pch_uart_hal_read(struct eg20t_port *priv, unsigned char *buf,
                        if (uart_handle_break(port))
                                continue;
                }
-               if (uart_handle_sysrq_char(port, rbr))
+               if (uart_prepare_sysrq_char(port, rbr))
                        continue;
 
                buf[i++] = rbr;
@@ -1070,7 +1070,7 @@ static irqreturn_t pch_uart_interrupt(int irq, void *dev_id)
                handled |= (unsigned int)ret;
        }
 
-       uart_port_unlock(&priv->port);
+       uart_unlock_and_check_sysrq(&priv->port);
        return IRQ_RETVAL(handled);
 }
 
@@ -1550,22 +1550,17 @@ pch_console_write(struct console *co, const char *s, unsigned int count)
 {
        struct eg20t_port *priv;
        unsigned long flags;
-       int port_locked = 1;
+       int locked = 1;
        u8 ier;
 
        priv = pch_uart_ports[co->index];
 
        touch_nmi_watchdog();
 
-       local_irq_save(flags);
-       if (priv->port.sysrq) {
-               /* serial8250_handle_port() already took the port lock */
-               port_locked = 0;
-       } else if (oops_in_progress) {
-               port_locked = uart_port_trylock(&priv->port);
-       } else {
-               uart_port_lock(&priv->port);
-       }
+       if (oops_in_progress)
+               locked = uart_port_trylock_irqsave(&priv->port, &flags);
+       else
+               uart_port_lock_irqsave(&priv->port, &flags);
 
        /*
         *      First save the IER then disable the interrupts
@@ -1583,9 +1578,8 @@ pch_console_write(struct console *co, const char *s, unsigned int count)
        wait_for_xmitr(priv, UART_LSR_BOTH_EMPTY);
        iowrite8(ier, priv->membase + UART_IER);
 
-       if (port_locked)
-               uart_port_unlock(&priv->port);
-       local_irq_restore(flags);
+       if (locked)
+               uart_port_unlock_irqrestore(&priv->port, flags);
 }
 
 static int __init pch_console_setup(struct console *co, char *options)