[PATCH v11 07/27] coresight: Take a reference on csdev

[Leo Yan]

coresight_get_ref() currently pins the provider module and takes a
reference on the parent device. That does not pin the CoreSight device
itself.

A driver can still be unbound while the CoreSight device is part of an
active trace path. In that case coresight_unregister() may release the
coresight_device while the path still holds its csdev pointer.

Take a reference on &csdev->dev when grabbing a CoreSight device and drop
it in coresight_put_ref().

Signed-off-by: Leo Yan <leo.yan at arm.com>
---
 drivers/hwtracing/coresight/coresight-core.c | 23 ++++++++++++++---------
 1 file changed, 14 insertions(+), 9 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-core.c b/drivers/hwtracing/coresight/coresight-core.c
index 5519d323f21f38d719b9030c7d77a9a61948ba1d..1a389f63ed006e054dc6bc9764f8be8c1def9da1 100644
--- a/drivers/hwtracing/coresight/coresight-core.c
+++ b/drivers/hwtracing/coresight/coresight-core.c
@@ -651,14 +651,18 @@ struct coresight_device *coresight_get_sink_by_id(u32 id)
  */
 static bool coresight_get_ref(struct coresight_device *csdev)
 {
-	struct device *dev = csdev->dev.parent;
+	struct device *parent = csdev->dev.parent;
 
 	/* Make sure the driver can't be removed */
-	if (!try_module_get(dev->driver->owner))
+	if (!try_module_get(parent->driver->owner))
 		return false;
-	/* Make sure the device can't go away */
-	get_device(dev);
-	pm_runtime_get_sync(dev);
+
+	/* Make sure parent device can't go away and is powered on */
+	get_device(parent);
+	pm_runtime_get_sync(parent);
+
+	/* Make sure csdev can't go away */
+	get_device(&csdev->dev);
 	return true;
 }
 
@@ -670,11 +674,12 @@ static bool coresight_get_ref(struct coresight_device *csdev)
  */
 static void coresight_put_ref(struct coresight_device *csdev)
 {
-	struct device *dev = csdev->dev.parent;
+	struct device *parent = csdev->dev.parent;
 
-	pm_runtime_put(dev);
-	put_device(dev);
-	module_put(dev->driver->owner);
+	put_device(&csdev->dev);
+	pm_runtime_put(parent);
+	put_device(parent);
+	module_put(parent->driver->owner);
 }
 
 /*

-- 
2.34.1