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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Fri, 1 Mar 2024 22:45:31 +0100
Subject: [PATCH 18/18] serial: pch: Use uart_prepare_sysrq_char().
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/6.8/older/patches-6.8.2-rt11.tar.xz
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.
Link: https://lore.kernel.org/r/20240301215246.891055-19-bigeasy@linutronix.de
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
drivers/tty/serial/pch_uart.c | 24 +++++++++---------------
1 file changed, 9 insertions(+), 15 deletions(-)
--- 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 eg20
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(in
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, co
{
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, co
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)
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