serial: lpc32xx_hs: Use uart_prepare_sysrq_char() to handle sysrq.

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.

Handle sysrq requests sysrq once the port lock is dropped.
Remove the special case in the console write routine an always use the
complete locking function.

Cc: Vladimir Zapolskiy <vz@mleia.com>
Cc: linux-arm-kernel@lists.infradead.org
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Link: https://lore.kernel.org/r/20240301215246.891055-10-bigeasy@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/lpc32xx_hs.c b/drivers/tty/serial/lpc32xx_hs.c
index 269efc5e2d51f7c34949a7d984436a85b7e7884f..3e4ac46de1bc3786173c72754e0240965aec183c 100644 (file)
--- a/drivers/tty/serial/lpc32xx_hs.c
+++ b/drivers/tty/serial/lpc32xx_hs.c
@@ -136,20 +136,16 @@ static void lpc32xx_hsuart_console_write(struct console *co, const char *s,
        int locked = 1;
 
        touch_nmi_watchdog();
-       local_irq_save(flags);
-       if (up->port.sysrq)
-               locked = 0;
-       else if (oops_in_progress)
-               locked = uart_port_trylock(&up->port);
+       if (oops_in_progress)
+               locked = uart_port_trylock_irqsave(&up->port, &flags);
        else
-               uart_port_lock(&up->port);
+               uart_port_lock_irqsave(&up->port, &flags);
 
        uart_console_write(&up->port, s, count, lpc32xx_hsuart_console_putchar);
        wait_for_xmit_empty(&up->port);
 
        if (locked)
-               uart_port_unlock(&up->port);
-       local_irq_restore(flags);
+               uart_port_unlock_irqrestore(&up->port, flags);
 }
 
 static int __init lpc32xx_hsuart_console_setup(struct console *co,
@@ -266,7 +262,8 @@ static void __serial_lpc32xx_rx(struct uart_port *port)
                        tty_insert_flip_char(tport, 0, TTY_FRAME);
                }
 
-               tty_insert_flip_char(tport, (tmp & 0xFF), flag);
+               if (!uart_prepare_sysrq_char(port, tmp & 0xff))
+                       tty_insert_flip_char(tport, (tmp & 0xFF), flag);
 
                tmp = readl(LPC32XX_HSUART_FIFO(port->membase));
        }
@@ -331,7 +328,7 @@ static irqreturn_t serial_lpc32xx_interrupt(int irq, void *dev_id)
                __serial_lpc32xx_tx(port);
        }
 
-       uart_port_unlock(port);
+       uart_unlock_and_check_sysrq(port);
 
        return IRQ_HANDLED;
 }