FAILED: patch "[PATCH] serial: fix TIOCMIWAIT race" failed to apply to 5.15-stable tree

The patch below does not apply to the 5.15-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x 40adffec8c0090533dfaa863ced7901b60bbf1dc
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026100502-seducing-scabbed-7835@gregkh' --subject-prefix 'PATCH 5.15.y' 'HEAD^..'

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 40adffec8c0090533dfaa863ced7901b60bbf1dc Mon Sep 17 00:00:00 2001
From: Johan Hovold <[email protected]>
Date: Thu, 10 Sep 2026 15:08:15 +0200
Subject: [PATCH] serial: fix TIOCMIWAIT race

The task state must be updated before checking the wakeup condition to avoid missing a racing modem status update.

index 139b93876229..f7b30f77b231 100644
@@ -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)) ||

From: Johan Hovold <[email protected]>

[ Upstream commit 40adffec8c0090533dfaa863ced7901b60bbf1dc ]

The task state must be updated before checking the wakeup condition to avoid missing a racing modem status update.

---
 drivers/tty/serial/serial_core.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

index 404354727d194..1cba822e068e9 100644
@@ -1213,12 +1213,12 @@ static int uart_wait_modem_status(struct uart_state *state, unsigned long arg)
 
 	add_wait_queue(&port->delta_msr_wait, &wait);
 	for (;;) {
+		set_current_state(TASK_INTERRUPTIBLE);
+
 		spin_lock_irq(&uport->lock);
 		memcpy(&cnow, &uport->icount, sizeof(struct uart_icount));
 		spin_unlock_irq(&uport->lock);
 
-		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)) ||

2.53.0