Commit d47dd323 authored by Sebastian Andrzej Siewior's avatar Sebastian Andrzej Siewior Committed by Greg Kroah-Hartman
Browse files

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: default avatarSebastian Andrzej Siewior <bigeasy@linutronix.de>
Link: https://lore.kernel.org/r/20240301215246.891055-19-bigeasy@linutronix.de


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 06d28ca0

drivers/tty/serial/pch_uart.c

+9 −15
Original line number Diff line number Diff line
@@ -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)