Commit 6ba52968 authored by Sebastian Andrzej Siewior's avatar Sebastian Andrzej Siewior Committed by Greg Kroah-Hartman
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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: default avatarSebastian Andrzej Siewior <bigeasy@linutronix.de>
Link: https://lore.kernel.org/r/20240301215246.891055-10-bigeasy@linutronix.de


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent e544127c

drivers/tty/serial/lpc32xx_hs.c

+7 −10
Original line number Diff line number Diff line
@@ -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,
@@ -266,6 +262,7 @@ static void __serial_lpc32xx_rx(struct uart_port *port) 
			tty_insert_flip_char(tport, 0, TTY_FRAME);

		}



		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;

}