commit 039d4926379b ("serial: 8250: Toggle IER bits on only after irq has been set up") moved IRQ setup before the THRE test, so the interrupt handler can run during the test and race with its IIR reads. This can produce wrong THRE test results and cause spurious registration of the serial8250_backup_timeout timer. Unconditionally disable the IRQ for the short duration of the test and re-enable it afterwards to avoid the race.

Cc: stable@vger.kernel.org Fixes: 039d4926379b ("serial: 8250: Toggle IER bits on only after irq has been set up") Signed-off-by: Peng Zhang zhangpeng.00@bytedance.com --- drivers/tty/serial/8250/8250_port.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c index 719faf92aa8a..f1740cc91143 100644 --- a/drivers/tty/serial/8250/8250_port.c +++ b/drivers/tty/serial/8250/8250_port.c @@ -2147,8 +2147,7 @@ static void serial8250_THRE_test(struct uart_port *port) if (up->port.flags & UPF_NO_THRE_TEST) return;

- if (port->irqflags & IRQF_SHARED) - disable_irq_nosync(port->irq); + disable_irq(port->irq);

/* * Test for UARTs that do not reassert THRE when the transmitter is idle and the interrupt @@ -2170,8 +2169,7 @@ static void serial8250_THRE_test(struct uart_port *port) serial_port_out(port, UART_IER, 0); }

- if (port->irqflags & IRQF_SHARED) - enable_irq(port->irq); + enable_irq(port->irq);

/* * If the interrupt is not reasserted, or we otherwise don't trust the iir, setup a timer to