[PATCH v4 3/4] serial: fix TIOCMIWAIT race
From: Johan Hovold <johan@kernel.org>
Date: 2026-09-10 13:08:28
Also in:
lkml, stable
Subsystem:
the rest, tty layer and serial drivers · Maintainers:
Linus Torvalds, Greg Kroah-Hartman, Jiri Slaby
The task state must be updated before checking the wakeup condition to
avoid missing a racing modem status update.
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Reported-by: sashiko-bot@kernel.org
Link: https://lore.kernel.org/r/20260904115542.E20D11F00A3D@smtp.kernel.org (local)
Cc: stable@vger.kernel.org
Signed-off-by: Johan Hovold <johan@kernel.org>
---
drivers/tty/serial/serial_core.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index 139b93876229..f7b30f77b231 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c@@ -1230,12 +1230,12 @@ static int uart_wait_modem_status(struct tty_struct *tty, struct uart_state *sta add_wait_queue(&port->delta_msr_wait, &wait); for (;;) { + set_current_state(TASK_INTERRUPTIBLE); + uart_port_lock_irq(uport); memcpy(&cnow, &uport->icount, sizeof(struct uart_icount)); uart_port_unlock_irq(uport); - set_current_state(TASK_INTERRUPTIBLE); - if (((arg & TIOCM_RNG) && (cnow.rng != cprev.rng)) || ((arg & TIOCM_DSR) && (cnow.dsr != cprev.dsr)) || ((arg & TIOCM_CD) && (cnow.dcd != cprev.dcd)) ||
--
2.55.0