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* FAILED: patch "[PATCH] usb: typec: ucsi: displayport: Fix deadlock" failed to apply to 5.15-stable tree
@ 2025-05-12 10:43 gregkh
  2025-05-14 15:01 ` [PATCH 5.15.y] usb: typec: ucsi: displayport: Fix deadlock Andrei Kuchynski
  2025-05-19  9:43 ` Andrei Kuchynski
  0 siblings, 2 replies; 5+ messages in thread
From: gregkh @ 2025-05-12 10:43 UTC (permalink / raw)
  To: akuchynski, gregkh, heikki.krogerus, stable; +Cc: stable


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 <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-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x 364618c89d4c57c85e5fc51a2446cd939bf57802
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2025051221-pacifist-liability-19cf@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^..

Possible dependencies:



thanks,

greg k-h

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

From 364618c89d4c57c85e5fc51a2446cd939bf57802 Mon Sep 17 00:00:00 2001
From: Andrei Kuchynski <akuchynski@chromium.org>
Date: Thu, 24 Apr 2025 08:44:28 +0000
Subject: [PATCH] usb: typec: ucsi: displayport: Fix deadlock

This patch introduces the ucsi_con_mutex_lock / ucsi_con_mutex_unlock
functions to the UCSI driver. ucsi_con_mutex_lock ensures the connector
mutex is only locked if a connection is established and the partner pointer
is valid. This resolves a deadlock scenario where
ucsi_displayport_remove_partner holds con->mutex waiting for
dp_altmode_work to complete while dp_altmode_work attempts to acquire it.

Cc: stable <stable@kernel.org>
Fixes: af8622f6a585 ("usb: typec: ucsi: Support for DisplayPort alt mode")
Signed-off-by: Andrei Kuchynski <akuchynski@chromium.org>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Link: https://lore.kernel.org/r/20250424084429.3220757-2-akuchynski@chromium.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/typec/ucsi/displayport.c b/drivers/usb/typec/ucsi/displayport.c
index 420af5139c70..acd053d4e38c 100644
--- a/drivers/usb/typec/ucsi/displayport.c
+++ b/drivers/usb/typec/ucsi/displayport.c
@@ -54,7 +54,8 @@ static int ucsi_displayport_enter(struct typec_altmode *alt, u32 *vdo)
 	u8 cur = 0;
 	int ret;
 
-	mutex_lock(&dp->con->lock);
+	if (!ucsi_con_mutex_lock(dp->con))
+		return -ENOTCONN;
 
 	if (!dp->override && dp->initialized) {
 		const struct typec_altmode *p = typec_altmode_get_partner(alt);
@@ -100,7 +101,7 @@ static int ucsi_displayport_enter(struct typec_altmode *alt, u32 *vdo)
 	schedule_work(&dp->work);
 	ret = 0;
 err_unlock:
-	mutex_unlock(&dp->con->lock);
+	ucsi_con_mutex_unlock(dp->con);
 
 	return ret;
 }
@@ -112,7 +113,8 @@ static int ucsi_displayport_exit(struct typec_altmode *alt)
 	u64 command;
 	int ret = 0;
 
-	mutex_lock(&dp->con->lock);
+	if (!ucsi_con_mutex_lock(dp->con))
+		return -ENOTCONN;
 
 	if (!dp->override) {
 		const struct typec_altmode *p = typec_altmode_get_partner(alt);
@@ -144,7 +146,7 @@ static int ucsi_displayport_exit(struct typec_altmode *alt)
 	schedule_work(&dp->work);
 
 out_unlock:
-	mutex_unlock(&dp->con->lock);
+	ucsi_con_mutex_unlock(dp->con);
 
 	return ret;
 }
@@ -202,20 +204,21 @@ static int ucsi_displayport_vdm(struct typec_altmode *alt,
 	int cmd = PD_VDO_CMD(header);
 	int svdm_version;
 
-	mutex_lock(&dp->con->lock);
+	if (!ucsi_con_mutex_lock(dp->con))
+		return -ENOTCONN;
 
 	if (!dp->override && dp->initialized) {
 		const struct typec_altmode *p = typec_altmode_get_partner(alt);
 
 		dev_warn(&p->dev,
 			 "firmware doesn't support alternate mode overriding\n");
-		mutex_unlock(&dp->con->lock);
+		ucsi_con_mutex_unlock(dp->con);
 		return -EOPNOTSUPP;
 	}
 
 	svdm_version = typec_altmode_get_svdm_version(alt);
 	if (svdm_version < 0) {
-		mutex_unlock(&dp->con->lock);
+		ucsi_con_mutex_unlock(dp->con);
 		return svdm_version;
 	}
 
@@ -259,7 +262,7 @@ static int ucsi_displayport_vdm(struct typec_altmode *alt,
 		break;
 	}
 
-	mutex_unlock(&dp->con->lock);
+	ucsi_con_mutex_unlock(dp->con);
 
 	return 0;
 }
diff --git a/drivers/usb/typec/ucsi/ucsi.c b/drivers/usb/typec/ucsi/ucsi.c
index e8c7e9dc4930..01ce858a1a2b 100644
--- a/drivers/usb/typec/ucsi/ucsi.c
+++ b/drivers/usb/typec/ucsi/ucsi.c
@@ -1922,6 +1922,40 @@ void ucsi_set_drvdata(struct ucsi *ucsi, void *data)
 }
 EXPORT_SYMBOL_GPL(ucsi_set_drvdata);
 
+/**
+ * ucsi_con_mutex_lock - Acquire the connector mutex
+ * @con: The connector interface to lock
+ *
+ * Returns true on success, false if the connector is disconnected
+ */
+bool ucsi_con_mutex_lock(struct ucsi_connector *con)
+{
+	bool mutex_locked = false;
+	bool connected = true;
+
+	while (connected && !mutex_locked) {
+		mutex_locked = mutex_trylock(&con->lock) != 0;
+		connected = UCSI_CONSTAT(con, CONNECTED);
+		if (connected && !mutex_locked)
+			msleep(20);
+	}
+
+	connected = connected && con->partner;
+	if (!connected && mutex_locked)
+		mutex_unlock(&con->lock);
+
+	return connected;
+}
+
+/**
+ * ucsi_con_mutex_unlock - Release the connector mutex
+ * @con: The connector interface to unlock
+ */
+void ucsi_con_mutex_unlock(struct ucsi_connector *con)
+{
+	mutex_unlock(&con->lock);
+}
+
 /**
  * ucsi_create - Allocate UCSI instance
  * @dev: Device interface to the PPM (Platform Policy Manager)
diff --git a/drivers/usb/typec/ucsi/ucsi.h b/drivers/usb/typec/ucsi/ucsi.h
index 3a2c1762bec1..9c5278a0c5d4 100644
--- a/drivers/usb/typec/ucsi/ucsi.h
+++ b/drivers/usb/typec/ucsi/ucsi.h
@@ -94,6 +94,8 @@ int ucsi_register(struct ucsi *ucsi);
 void ucsi_unregister(struct ucsi *ucsi);
 void *ucsi_get_drvdata(struct ucsi *ucsi);
 void ucsi_set_drvdata(struct ucsi *ucsi, void *data);
+bool ucsi_con_mutex_lock(struct ucsi_connector *con);
+void ucsi_con_mutex_unlock(struct ucsi_connector *con);
 
 void ucsi_connector_change(struct ucsi *ucsi, u8 num);
 


^ permalink raw reply related	[flat|nested] 5+ messages in thread
end of thread, other threads:[~2025-05-20  7:52 UTC | newest]

Thread overview: 5+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2025-05-12 10:43 FAILED: patch "[PATCH] usb: typec: ucsi: displayport: Fix deadlock" failed to apply to 5.15-stable tree gregkh
2025-05-14 15:01 ` [PATCH 5.15.y] usb: typec: ucsi: displayport: Fix deadlock Andrei Kuchynski
2025-05-15  0:28   ` Sasha Levin
2025-05-19  9:43 ` Andrei Kuchynski
2025-05-20  7:52   ` Sasha Levin

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