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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Fri, 1 Mar 2024 22:45:16 +0100
Subject: [PATCH 03/18] serial: bcm63xx: 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/20240301215246.891055-4-bigeasy@linutronix.de
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
drivers/tty/serial/bcm63xx_uart.c | 24 ++++++++----------------
1 file changed, 8 insertions(+), 16 deletions(-)
--- a/drivers/tty/serial/bcm63xx_uart.c
+++ b/drivers/tty/serial/bcm63xx_uart.c
@@ -285,10 +285,9 @@ static void bcm_uart_do_rx(struct uart_p
flag = TTY_PARITY;
}
- if (uart_handle_sysrq_char(port, c))
+ if (uart_prepare_sysrq_char(port, c))
continue;
-
if ((cstat & port->ignore_status_mask) == 0)
tty_insert_flip_char(tty_port, c, flag);
@@ -353,7 +352,7 @@ static irqreturn_t bcm_uart_interrupt(in
estat & UART_EXTINP_DCD_MASK);
}
- uart_port_unlock(port);
+ uart_unlock_and_check_sysrq(port);
return IRQ_HANDLED;
}
@@ -703,20 +702,14 @@ static void bcm_console_write(struct con
{
struct uart_port *port;
unsigned long flags;
- int locked;
+ int locked = 1;
port = &ports[co->index];
- local_irq_save(flags);
- if (port->sysrq) {
- /* bcm_uart_interrupt() already took the lock */
- locked = 0;
- } else if (oops_in_progress) {
- locked = uart_port_trylock(port);
- } else {
- uart_port_lock(port);
- locked = 1;
- }
+ if (oops_in_progress)
+ locked = uart_port_trylock_irqsave(port, &flags);
+ else
+ uart_port_lock_irqsave(port, &flags);
/* call helper to deal with \r\n */
uart_console_write(port, s, count, bcm_console_putchar);
@@ -725,8 +718,7 @@ static void bcm_console_write(struct con
wait_for_xmitr(port);
if (locked)
- uart_port_unlock(port);
- local_irq_restore(flags);
+ uart_port_unlock_irqrestore(port, flags);
}
/*
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