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Message-ID: <20250424084429.3220757-2-akuchynski@chromium.org>
Date: Thu, 24 Apr 2025 08:44:28 +0000
From: Andrei Kuchynski <akuchynski@...omium.org>
To: Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Jameson Thies <jthies@...gle.com>,
Abhishek Pandit-Subedi <abhishekpandit@...omium.org>,
Benson Leung <bleung@...omium.org>,
Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>,
Diogo Ivo <diogo.ivo@...nico.ulisboa.pt>,
Pooja Katiyar <pooja.katiyar@...el.com>,
Madhu M <madhu.m@...el.com>
Cc: linux-usb@...r.kernel.org,
linux-kernel@...r.kernel.org,
Andrei Kuchynski <akuchynski@...omium.org>,
stable@...r.kernel.org
Subject: [PATCH v2 1/2] 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@...r.kernel.org
Fixes: af8622f6a585 ("usb: typec: ucsi: Support for DisplayPort alt mode")
Signed-off-by: Andrei Kuchynski <akuchynski@...omium.org>
---
drivers/usb/typec/ucsi/displayport.c | 19 +++++++++-------
drivers/usb/typec/ucsi/ucsi.c | 34 ++++++++++++++++++++++++++++
drivers/usb/typec/ucsi/ucsi.h | 2 ++
3 files changed, 47 insertions(+), 8 deletions(-)
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);
--
2.49.0.805.g082f7c87e0-goog
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