[PATCH v11 06/24] coresight: add try_get_module() in coresight_grab_device()

Tingwei Zhang
2020-09-15T10:43:13Z

When coresight device is in an active session, driver module of
that device should not be removed. Use try_get_module() in
coresight_grab_device() to prevent module to be unloaded.
Use get_device()/put_device() to protect device data
in the middle of active session.

Signed-off-by: Tingwei Zhang <tingwei@codeaurora.org>
Tested-by: Mike Leach <mike.leach@linaro.org>
Suggested-by: Suzuki K Poulose <suzuki.poulose@arm.com>
---
drivers/hwtracing/coresight/coresight.c | 60 ++++++++++++++++++++++---
1 file changed, 53 insertions(+), 7 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight.c b/drivers/hwtracing/coresight/coresight.c
index d1aea3a1e7b6..4faa4aa3964d 100644
--- a/drivers/hwtracing/coresight/coresight.c
+++ b/drivers/hwtracing/coresight/coresight.c
@@ -629,13 +629,45 @@ struct coresight_device *coresight_get_sink_by_id(u32 id)
return dev ? to_coresight_device(dev) : NULL;
}

+/**
+ * coresight_get_ref- Helper function to increase reference count to module
+ * and device.
+ * Return true in successful case and power up the device.
+ * Return false when failed to get reference of module.
+ */
+static inline bool coresight_get_ref(struct coresight_device *csdev)
+{
+ struct device *dev = csdev->dev.parent;
+
+ /* Make sure the driver can't be removed */
+ if (!try_module_get(dev->driver->owner))
+ return false;
+ /* Make sure the device can't go away */
+ get_device(dev);
+ pm_runtime_get_sync(dev);
+ return true;
+}
+
+/**
+ * coresight_put_ref- Helper function to decrease reference count to module
+ * and device. Power off the device.
+ */
+static inline void coresight_put_ref(struct coresight_device *csdev)
+{
+ struct device *dev = csdev->dev.parent;
+
+ pm_runtime_put(dev);
+ put_device(dev);
+ module_put(dev->driver->owner);
+}
+
/*
* coresight_grab_device - Power up this device and any of the helper
* devices connected to it for trace operation. Since the helper devices
* don't appear on the trace path, they should be handled along with the
* the master device.
*/
-static void coresight_grab_device(struct coresight_device *csdev)
+static int coresight_grab_device(struct coresight_device *csdev)
{
int i;

@@ -644,9 +676,20 @@ static void coresight_grab_device(struct coresight_device *csdev)

child = csdev->pdata->conns[i].child_dev;
if (child && child->type == CORESIGHT_DEV_TYPE_HELPER)
- pm_runtime_get_sync(child->dev.parent);
+ if (!coresight_get_ref(child))
+ goto err;
+ }
+ if (coresight_get_ref(csdev))
+ return 0;
+err:
+ for (i--; i >= 0; i--) {
+ struct coresight_device *child;
+
+ child = csdev->pdata->conns[i].child_dev;
+ if (child && child->type == CORESIGHT_DEV_TYPE_HELPER)
+ coresight_put_ref(child);
}
- pm_runtime_get_sync(csdev->dev.parent);
+ return -ENODEV;
}

/*
@@ -657,13 +700,13 @@ static void coresight_drop_device(struct coresight_device *csdev)
{
int i;

- pm_runtime_put(csdev->dev.parent);
+ coresight_put_ref(csdev);
for (i = 0; i < csdev->pdata->nr_outport; i++) {
struct coresight_device *child;

child = csdev->pdata->conns[i].child_dev;
if (child && child->type == CORESIGHT_DEV_TYPE_HELPER)
- pm_runtime_put(child->dev.parent);
+ coresight_put_ref(child);
}
}

@@ -682,7 +725,7 @@ static int _coresight_build_path(struct coresight_device *csdev,
struct coresight_device *sink,
struct list_head *path)
{
- int i;
+ int i, ret;
bool found = false;
struct coresight_node *node;

@@ -712,11 +755,14 @@ static int _coresight_build_path(struct coresight_device *csdev,
* is tell the PM runtime core we need this element and add a node
* for it.
*/
+ ret = coresight_grab_device(csdev);
+ if (ret)
+ return ret;
+
node = kzalloc(sizeof(struct coresight_node), GFP_KERNEL);
if (!node)
return -ENOMEM;

- coresight_grab_device(csdev);
node->csdev = csdev;
list_add(&node->link, path);