From: Sebastian Andrzej Siewior Date: Fri, 1 Mar 2024 22:45:19 +0100 Subject: [PATCH 06/18] serial: omap: 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/20240301215246.891055-7-bigeasy@linutronix.de Signed-off-by: Sebastian Andrzej Siewior --- drivers/tty/serial/omap-serial.c | 16 ++++++---------- 1 file changed, 6 insertions(+), 10 deletions(-) --- a/drivers/tty/serial/omap-serial.c +++ b/drivers/tty/serial/omap-serial.c @@ -508,7 +508,7 @@ static void serial_omap_rdi(struct uart_ up->port.icount.rx++; - if (uart_handle_sysrq_char(&up->port, ch)) + if (uart_prepare_sysrq_char(&up->port, ch)) return; uart_insert_char(&up->port, lsr, UART_LSR_OE, ch, TTY_NORMAL); @@ -563,7 +563,7 @@ static irqreturn_t serial_omap_irq(int i } } while (max_count--); - uart_port_unlock(&up->port); + uart_unlock_and_check_sysrq(&up->port); tty_flip_buffer_push(&up->port.state->port); @@ -1212,13 +1212,10 @@ serial_omap_console_write(struct console unsigned int ier; 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 @@ -1245,8 +1242,7 @@ serial_omap_console_write(struct console check_modem_status(up); if (locked) - uart_port_unlock(&up->port); - local_irq_restore(flags); + uart_port_unlock_irqrestore(&up->port, flags); } static int __init