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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Fri, 1 Mar 2024 22:45:22 +0100
Subject: [PATCH 09/18] serial: lpc32xx_hs: Use uart_prepare_sysrq_char() to
handle sysrq.
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.
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
Link: https://lore.kernel.org/r/20240301215246.891055-10-bigeasy@linutronix.de
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
drivers/tty/serial/lpc32xx_hs.c | 17 +++++++----------
1 file changed, 7 insertions(+), 10 deletions(-)
--- a/drivers/tty/serial/lpc32xx_hs.c
+++ b/drivers/tty/serial/lpc32xx_hs.c
@@ -136,20 +136,16 @@ static void lpc32xx_hsuart_console_write
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,
@@ -268,7 +264,8 @@ static void __serial_lpc32xx_rx(struct u
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));
}
@@ -333,7 +330,7 @@ static irqreturn_t serial_lpc32xx_interr
__serial_lpc32xx_tx(port);
}
- uart_port_unlock(port);
+ uart_unlock_and_check_sysrq(port);
return IRQ_HANDLED;
}
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