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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Fri, 1 Mar 2024 22:45:15 +0100
Subject: [PATCH 02/18] serial: ar933x: 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/20240301215246.891055-3-bigeasy@linutronix.de
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
drivers/tty/serial/ar933x_uart.c | 18 ++++++------------
1 file changed, 6 insertions(+), 12 deletions(-)
--- a/drivers/tty/serial/ar933x_uart.c
+++ b/drivers/tty/serial/ar933x_uart.c
@@ -378,7 +378,7 @@ static void ar933x_uart_rx_chars(struct
up->port.icount.rx++;
ch = rdata & AR933X_UART_DATA_TX_RX_MASK;
- if (uart_handle_sysrq_char(&up->port, ch))
+ if (uart_prepare_sysrq_char(&up->port, ch))
continue;
if ((up->port.ignore_status_mask & AR933X_DUMMY_STATUS_RD) == 0)
@@ -468,7 +468,7 @@ static irqreturn_t ar933x_uart_interrupt
ar933x_uart_tx_chars(up);
}
- uart_port_unlock(&up->port);
+ uart_unlock_and_check_sysrq(&up->port);
return IRQ_HANDLED;
}
@@ -627,14 +627,10 @@ static void ar933x_uart_console_write(st
unsigned int int_en;
int locked = 1;
- 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);
/*
* First save the IER then disable the interrupts
@@ -654,9 +650,7 @@ static void ar933x_uart_console_write(st
ar933x_uart_write(up, AR933X_UART_INT_REG, AR933X_UART_INT_ALLINTS);
if (locked)
- uart_port_unlock(&up->port);
-
- local_irq_restore(flags);
+ uart_port_unlock_irqrestore(&up->port, flags);
}
static int ar933x_uart_console_setup(struct console *co, char *options)
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