[PATCH net 2/3] dpll: zl3073x: use __dpll_device_change_ntf() and remove change_work

[Ivan Vecera]

The change_work was introduced to send device change notifications
from DPLL device callbacks without deadlocking on dpll_lock, since
the callbacks are already invoked under that lock. Now that
__dpll_device_change_ntf() is exported for callers that already
hold dpll_lock, use it directly and remove the change_work
infrastructure entirely.

This eliminates a race condition where change_work could be
re-scheduled after cancel_work_sync() during device teardown,
potentially causing the handler to dereference a freed or NULL
dpll_dev pointer.

Fixes: 9363b4837659 ("dpll: zl3073x: Allow to configure phase offset averaging factor")
Signed-off-by: Ivan Vecera <ivecera@xxxxxxxxxx>
---
 drivers/dpll/zl3073x/dpll.c | 26 +++++++++-----------------
 drivers/dpll/zl3073x/dpll.h |  2 --
 2 files changed, 9 insertions(+), 19 deletions(-)

diff --git a/drivers/dpll/zl3073x/dpll.c b/drivers/dpll/zl3073x/dpll.c
index 64b4e9e3e8fe..0770bd895de9 100644
--- a/drivers/dpll/zl3073x/dpll.c
+++ b/drivers/dpll/zl3073x/dpll.c
@@ -1079,15 +1079,6 @@ zl3073x_dpll_phase_offset_avg_factor_get(const struct dpll_device *dpll,
 	return 0;
 }
 
-static void
-zl3073x_dpll_change_work(struct work_struct *work)
-{
-	struct zl3073x_dpll *zldpll;
-
-	zldpll = container_of(work, struct zl3073x_dpll, change_work);
-	dpll_device_change_ntf(zldpll->dpll_dev);
-}
-
 static int
 zl3073x_dpll_phase_offset_avg_factor_set(const struct dpll_device *dpll,
 					 void *dpll_priv, u32 factor,
@@ -1113,8 +1104,10 @@ zl3073x_dpll_phase_offset_avg_factor_set(const struct dpll_device *dpll,
 	 * we have to send a notification for other DPLL devices.
 	 */
 	list_for_each_entry(item, &zldpll->dev->dplls, list) {
-		if (item != zldpll)
-			schedule_work(&item->change_work);
+		struct dpll_device *dpll_dev = READ_ONCE(item->dpll_dev);
+
+		if (item != zldpll && dpll_dev)
+			__dpll_device_change_ntf(dpll_dev);
 	}
 
 	return 0;
@@ -1627,13 +1620,13 @@ zl3073x_dpll_device_register(struct zl3073x_dpll *zldpll)
 static void
 zl3073x_dpll_device_unregister(struct zl3073x_dpll *zldpll)
 {
-	WARN(!zldpll->dpll_dev, "DPLL device is not registered\n");
+	struct dpll_device *dpll_dev = READ_ONCE(zldpll->dpll_dev);
 
-	cancel_work_sync(&zldpll->change_work);
+	WARN(!dpll_dev, "DPLL device is not registered\n");
 
-	dpll_device_unregister(zldpll->dpll_dev, &zldpll->ops, zldpll);
-	dpll_device_put(zldpll->dpll_dev, &zldpll->tracker);
-	zldpll->dpll_dev = NULL;
+	WRITE_ONCE(zldpll->dpll_dev, NULL);
+	dpll_device_unregister(dpll_dev, &zldpll->ops, zldpll);
+	dpll_device_put(dpll_dev, &zldpll->tracker);
 }
 
 /**
@@ -1926,7 +1919,6 @@ zl3073x_dpll_alloc(struct zl3073x_dev *zldev, u8 ch)
 	zldpll->dev = zldev;
 	zldpll->id = ch;
 	INIT_LIST_HEAD(&zldpll->pins);
-	INIT_WORK(&zldpll->change_work, zl3073x_dpll_change_work);
 
 	return zldpll;
 }
diff --git a/drivers/dpll/zl3073x/dpll.h b/drivers/dpll/zl3073x/dpll.h
index 434c32a7db12..c8bc8437a709 100644
--- a/drivers/dpll/zl3073x/dpll.h
+++ b/drivers/dpll/zl3073x/dpll.h
@@ -21,7 +21,6 @@
  * @tracker: tracking object for the acquired reference
  * @lock_status: last saved DPLL lock status
  * @pins: list of pins
- * @change_work: device change notification work
  */
 struct zl3073x_dpll {
 	struct list_head		list;
@@ -35,7 +34,6 @@ struct zl3073x_dpll {
 	dpll_tracker			tracker;
 	enum dpll_lock_status		lock_status;
 	struct list_head		pins;
-	struct work_struct		change_work;
 };
 
 struct zl3073x_dpll *zl3073x_dpll_alloc(struct zl3073x_dev *zldev, u8 ch);
-- 
2.53.0