From: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Date: Fri, 1 Mar 2024 22:45:21 +0100 Subject: [PATCH 08/18] serial: sunplus: Use uart_prepare_sysrq_char(). 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. Cc: Hammer Hsieh <hammerh0314@gmail.com> Link: https://lore.kernel.org/r/20240301215246.891055-9-bigeasy@linutronix.de Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> --- drivers/tty/serial/sunplus-uart.c | 18 ++++++------------ 1 file changed, 6 insertions(+), 12 deletions(-) Index: linux-6.8.2-rt10/drivers/tty/serial/sunplus-uart.c =================================================================== @ linux-6.8.2-rt10/drivers/tty/serial/sunplus-uart.c:263 @ static void receive_chars(struct uart_po if (port->ignore_status_mask & SUP_DUMMY_READ) goto ignore_char; - if (uart_handle_sysrq_char(port, ch)) + if (uart_prepare_sysrq_char(port, ch)) goto ignore_char; uart_insert_char(port, lsr, SUP_UART_LSR_OE, ch, flag); @ linux-6.8.2-rt10/drivers/tty/serial/sunplus-uart.c:290 @ static irqreturn_t sunplus_uart_irq(int if (isc & SUP_UART_ISC_TX) transmit_chars(port); - uart_port_unlock(port); + uart_unlock_and_check_sysrq(port); return IRQ_HANDLED; } @ linux-6.8.2-rt10/drivers/tty/serial/sunplus-uart.c:515 @ static void sunplus_console_write(struct unsigned long flags; int locked = 1; - local_irq_save(flags); - - if (sunplus_console_ports[co->index]->port.sysrq) - locked = 0; - else if (oops_in_progress) - locked = uart_port_trylock(&sunplus_console_ports[co->index]->port); + if (oops_in_progress) + locked = uart_port_trylock_irqsave(&sunplus_console_ports[co->index]->port, &flags); else - uart_port_lock(&sunplus_console_ports[co->index]->port); + uart_port_lock_irqsave(&sunplus_console_ports[co->index]->port, &flags); uart_console_write(&sunplus_console_ports[co->index]->port, s, count, sunplus_uart_console_putchar); if (locked) - uart_port_unlock(&sunplus_console_ports[co->index]->port); - - local_irq_restore(flags); + uart_port_unlock_irqrestore(&sunplus_console_ports[co->index]->port, flags); } static int __init sunplus_console_setup(struct console *co, char *options)