FAILED: patch "[PATCH] xhci: dbgtty: fix device unregister" failed to apply to 5.10-stable tree

FAILED: patch "[PATCH] xhci: dbgtty: fix device unregister" failed to apply to 5.10-stable tree

[gregkh]

The patch below does not apply to the 5.10-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 <stable@vger.kernel.org>.

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-5.10.y
git checkout FETCH_HEAD
git cherry-pick -x 1f73b8b56cf35de29a433aee7bfff26cea98be3f
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2025120110-coastal-litigator-8952@gregkh' --subject-prefix 'PATCH 5.10.y' HEAD^..

Possible dependencies:



thanks,

greg k-h

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

From 1f73b8b56cf35de29a433aee7bfff26cea98be3f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=C5=81ukasz=20Bartosik?= <ukaszb@chromium.org>
Date: Wed, 19 Nov 2025 21:29:09 +0000
Subject: [PATCH] xhci: dbgtty: fix device unregister
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

When DbC is disconnected then xhci_dbc_tty_unregister_device()
is called. However if there is any user space process blocked
on write to DbC terminal device then it will never be signalled
and thus stay blocked indifinitely.

This fix adds a tty_vhangup() call in xhci_dbc_tty_unregister_device().
The tty_vhangup() wakes up any blocked writers and causes subsequent
write attempts to DbC terminal device to fail.

Cc: stable <stable@kernel.org>
Fixes: dfba2174dc42 ("usb: xhci: Add DbC support in xHCI driver")
Signed-off-by: Łukasz Bartosik <ukaszb@chromium.org>
Link: https://patch.msgid.link/20251119212910.1245694-1-ukaszb@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/host/xhci-dbgtty.c b/drivers/usb/host/xhci-dbgtty.c
index b7f95565524d..57cdda4e09c8 100644
--- a/drivers/usb/host/xhci-dbgtty.c
+++ b/drivers/usb/host/xhci-dbgtty.c
@@ -550,6 +550,12 @@ static void xhci_dbc_tty_unregister_device(struct xhci_dbc *dbc)
 
 	if (!port->registered)
 		return;
+	/*
+	 * Hang up the TTY. This wakes up any blocked
+	 * writers and causes subsequent writes to fail.
+	 */
+	tty_vhangup(port->port.tty);
+
 	tty_unregister_device(dbc_tty_driver, port->minor);
 	xhci_dbc_tty_exit_port(port);
 	port->registered = false;

[PATCH 5.10.y] xhci: dbgtty: fix device unregister

[Sasha Levin]

From: Łukasz Bartosik <ukaszb@chromium.org>

[ Upstream commit 1f73b8b56cf35de29a433aee7bfff26cea98be3f ]

When DbC is disconnected then xhci_dbc_tty_unregister_device()
is called. However if there is any user space process blocked
on write to DbC terminal device then it will never be signalled
and thus stay blocked indifinitely.

This fix adds a tty_vhangup() call in xhci_dbc_tty_unregister_device().
The tty_vhangup() wakes up any blocked writers and causes subsequent
write attempts to DbC terminal device to fail.

Cc: stable <stable@kernel.org>
Fixes: dfba2174dc42 ("usb: xhci: Add DbC support in xHCI driver")
Signed-off-by: Łukasz Bartosik <ukaszb@chromium.org>
Link: https://patch.msgid.link/20251119212910.1245694-1-ukaszb@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[ Adjust context ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/usb/host/xhci-dbgtty.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/usb/host/xhci-dbgtty.c b/drivers/usb/host/xhci-dbgtty.c
index 980235169d811..d03eea7beeca0 100644
--- a/drivers/usb/host/xhci-dbgtty.c
+++ b/drivers/usb/host/xhci-dbgtty.c
@@ -468,6 +468,12 @@ static void xhci_dbc_tty_unregister_device(struct xhci_dbc *dbc)
 
 	if (!port->registered)
 		return;
+	/*
+	 * Hang up the TTY. This wakes up any blocked
+	 * writers and causes subsequent writes to fail.
+	 */
+	tty_vhangup(port->port.tty);
+
 	tty_unregister_device(dbc_tty_driver, 0);
 	xhci_dbc_tty_exit_port(port);
 	port->registered = false;
-- 
2.51.0

Re: [PATCH 5.10.y] xhci: dbgtty: fix device unregister

[Łukasz Bartosik]

On Mon, Dec 8, 2025 at 2:01 PM Sasha Levin <sashal@kernel.org> wrote:
>
> From: Łukasz Bartosik <ukaszb@chromium.org>
>
> [ Upstream commit 1f73b8b56cf35de29a433aee7bfff26cea98be3f ]
>
> When DbC is disconnected then xhci_dbc_tty_unregister_device()
> is called. However if there is any user space process blocked
> on write to DbC terminal device then it will never be signalled
> and thus stay blocked indifinitely.
>
> This fix adds a tty_vhangup() call in xhci_dbc_tty_unregister_device().
> The tty_vhangup() wakes up any blocked writers and causes subsequent
> write attempts to DbC terminal device to fail.
>
> Cc: stable <stable@kernel.org>
> Fixes: dfba2174dc42 ("usb: xhci: Add DbC support in xHCI driver")
> Signed-off-by: Łukasz Bartosik <ukaszb@chromium.org>
> Link: https://patch.msgid.link/20251119212910.1245694-1-ukaszb@google.com
> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> [ Adjust context ]
> Signed-off-by: Sasha Levin <sashal@kernel.org>
> ---
>  drivers/usb/host/xhci-dbgtty.c | 6 ++++++
>  1 file changed, 6 insertions(+)
>
> diff --git a/drivers/usb/host/xhci-dbgtty.c b/drivers/usb/host/xhci-dbgtty.c
> index 980235169d811..d03eea7beeca0 100644
> --- a/drivers/usb/host/xhci-dbgtty.c
> +++ b/drivers/usb/host/xhci-dbgtty.c
> @@ -468,6 +468,12 @@ static void xhci_dbc_tty_unregister_device(struct xhci_dbc *dbc)
>
>         if (!port->registered)
>                 return;
> +       /*
> +        * Hang up the TTY. This wakes up any blocked
> +        * writers and causes subsequent writes to fail.
> +        */
> +       tty_vhangup(port->port.tty);
> +
>         tty_unregister_device(dbc_tty_driver, 0);
>         xhci_dbc_tty_exit_port(port);
>         port->registered = false;
> --
> 2.51.0
>

Thank you very much Sasha for resolving the conflict for me.

Regards,
Łukasz