Avoid locking in hard interrupt context, move the entirety of hard IRQ context code into the threaded IRQ handler. This fixes the following splat with preempt-rt enabled: BUG: scheduling while atomic: (mount)/1289/0x00010001 Modules linked in: Preemption disabled at: [<c0119127>] irq_enter_rcu+0xb/0x42 CPU: 0 PID: 1289 Comm: (mount) Not tainted 6.1.0-rc7-rt5-stable-standard-00006-gd70aeccb9f0f #17 Hardware name: STM32 (Device Tree Support) unwind_backtrace from show_stack+0xb/0xc show_stack from dump_stack_lvl+0x2b/0x34 dump_stack_lvl from __schedule_bug+0x53/0x80 __schedule_bug from __schedule+0x47/0x404 __schedule from schedule_rtlock+0x15/0x34 schedule_rtlock from rtlock_slowlock_locked+0x1d7/0x57e rtlock_slowlock_locked from rt_spin_lock+0x29/0x3c rt_spin_lock from stm32_usart_interrupt+0xa9/0x110 stm32_usart_interrupt from __handle_irq_event_percpu+0x73/0x14e __handle_irq_event_percpu from handle_irq_event_percpu+0x9/0x22 handle_irq_event_percpu from handle_irq_event+0x53/0x76 handle_irq_event from handle_fasteoi_irq+0x65/0xa8 handle_fasteoi_irq from handle_irq_desc+0xf/0x18 handle_irq_desc from gic_handle_irq+0x45/0x54 gic_handle_irq from generic_handle_arch_irq+0x19/0x2c generic_handle_arch_irq from call_with_stack+0xd/0x10 Signed-off-by: Marek Vasut <marex@xxxxxxx> --- Cc: Alexandre Torgue <alexandre.torgue@xxxxxxxxxxx> Cc: Erwan Le Ray <erwan.leray@xxxxxxxxxxx> Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> Cc: Jean Philippe Romain <jean-philippe.romain@xxxxxxxxxxx> Cc: Jiri Slaby <jirislaby@xxxxxxxxxx> Cc: Maxime Coquelin <mcoquelin.stm32@xxxxxxxxx> Cc: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: Valentin Caron <valentin.caron@xxxxxxxxxxx> Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx Cc: linux-stm32@xxxxxxxxxxxxxxxxxxxxxxxxxxxx To: linux-serial@xxxxxxxxxxxxxxx --- drivers/tty/serial/stm32-usart.c | 27 +++++++-------------------- 1 file changed, 7 insertions(+), 20 deletions(-) diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c index a1490033aa164..f5bce0be02676 100644 --- a/drivers/tty/serial/stm32-usart.c +++ b/drivers/tty/serial/stm32-usart.c @@ -745,14 +745,15 @@ static void stm32_usart_transmit_chars(struct uart_port *port) } } -static irqreturn_t stm32_usart_interrupt(int irq, void *ptr) +static irqreturn_t stm32_usart_threaded_interrupt(int irq, void *ptr) { struct uart_port *port = ptr; struct tty_port *tport = &port->state->port; struct stm32_port *stm32_port = to_stm32_port(port); const struct stm32_usart_offsets *ofs = &stm32_port->info->ofs; - u32 sr; + unsigned long flags; unsigned int size; + u32 sr; sr = readl_relaxed(port->membase + ofs->isr); @@ -792,27 +793,13 @@ static irqreturn_t stm32_usart_interrupt(int irq, void *ptr) } if ((sr & USART_SR_TXE) && !(stm32_port->tx_ch)) { - spin_lock(&port->lock); + spin_lock_irqsave(&port->lock, flags); stm32_usart_transmit_chars(port); - spin_unlock(&port->lock); + spin_unlock_irqrestore(&port->lock, flags); } - if (stm32_usart_rx_dma_enabled(port)) - return IRQ_WAKE_THREAD; - else - return IRQ_HANDLED; -} - -static irqreturn_t stm32_usart_threaded_interrupt(int irq, void *ptr) -{ - struct uart_port *port = ptr; - struct tty_port *tport = &port->state->port; - struct stm32_port *stm32_port = to_stm32_port(port); - unsigned int size; - unsigned long flags; - /* Receiver timeout irq for DMA RX */ - if (!stm32_port->throttled) { + if (stm32_usart_rx_dma_enabled(port) && !stm32_port->throttled) { spin_lock_irqsave(&port->lock, flags); size = stm32_usart_receive_chars(port, false); uart_unlock_and_check_sysrq_irqrestore(port, flags); @@ -1015,7 +1002,7 @@ static int stm32_usart_startup(struct uart_port *port) u32 val; int ret; - ret = request_threaded_irq(port->irq, stm32_usart_interrupt, + ret = request_threaded_irq(port->irq, NULL, stm32_usart_threaded_interrupt, IRQF_ONESHOT | IRQF_NO_SUSPEND, name, port); -- 2.35.1