[PATCH 07/13] serial: stm32: fix a deadlock in set_termios
From: Erwan Le Ray <hidden>
Date: 2021-02-19 17:51:25
Also in:
linux-arm-kernel, lkml
Subsystem:
the rest, tty layer and serial drivers · Maintainers:
Linus Torvalds, Greg Kroah-Hartman, Jiri Slaby
CTS/RTS GPIOs support that has been added recently to STM32 UART driver has
introduced scheduled code in a set_termios part protected by a spin lock.
This generates a potential deadlock scenario:
Chain exists of:
&irq_desc_lock_class --> console_owner --> &port_lock_key
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(&port_lock_key);
lock(console_owner);
lock(&port_lock_key);
lock(&irq_desc_lock_class);
*** DEADLOCK ***
4 locks held by stty/766:
Move the scheduled code after the spinlock.
Fixes: 6cf61b9bd7cc ("tty: serial: Add modem control gpio support for STM32 UART")
Signed-off-by: Erwan Le Ray <redacted>
diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c
index 14011183edfe..4ba164820904 100644
--- a/drivers/tty/serial/stm32-usart.c
+++ b/drivers/tty/serial/stm32-usart.c@@ -829,12 +829,6 @@ static void stm32_usart_set_termios(struct uart_port *port, cr3 |= USART_CR3_CTSE | USART_CR3_RTSE; } - /* Handle modem control interrupts */ - if (UART_ENABLE_MS(port, termios->c_cflag)) - stm32_usart_enable_ms(port); - else - stm32_usart_disable_ms(port); - usartdiv = DIV_ROUND_CLOSEST(port->uartclk, baud); /*
@@ -916,6 +910,12 @@ static void stm32_usart_set_termios(struct uart_port *port, stm32_usart_set_bits(port, ofs->cr1, BIT(cfg->uart_enable_bit)); spin_unlock_irqrestore(&port->lock, flags); + + /* Handle modem control interrupts */ + if (UART_ENABLE_MS(port, termios->c_cflag)) + stm32_usart_enable_ms(port); + else + stm32_usart_disable_ms(port); } static const char *stm32_usart_type(struct uart_port *port)
--
2.17.1