From: Erwan Le Ray erwan.leray@foss.st.com
[ Upstream commit 436c97936001776f16153771ee887f125443e974 ]
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 erwan.leray@foss.st.com Link: https://lore.kernel.org/r/20210304162308.8984-8-erwan.leray@foss.st.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/tty/serial/stm32-usart.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-)
diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c index 85e9a4d4e91d..44522ddc7e6d 100644 --- a/drivers/tty/serial/stm32-usart.c +++ b/drivers/tty/serial/stm32-usart.c @@ -827,12 +827,6 @@ 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);
/* @@ -914,6 +908,12 @@ 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)