Re: [PATCH v7 06/25] coresight: add try_get_module() in coresight_grab_device()

On 08/05/2020 03:54 AM, Tingwei Zhang wrote:

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

---

drivers/hwtracing/coresight/coresight.c | 39 +++++++++++++++++++++---- 1 file changed, 34 insertions(+), 5 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight.c b/drivers/hwtracing/coresight/coresight.c index b7151c5f81b1..1626bc885dfe 100644 --- a/drivers/hwtracing/coresight/coresight.c +++ b/drivers/hwtracing/coresight/coresight.c @@ -640,7 +640,7 @@ struct coresight_device *coresight_get_sink_by_id(u32 id)

• 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;

Please could you add a pair of helper functions to hold/drop reference to a device/driver ? i.e,

static inline bool coresight_get_ref(struct coresight_device *csdev) { struct device *dev = csdev->dev.parent;

/* Make sure the driver cant 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; }

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); }

@@ -648,10 +648,30 @@ static void coresight_grab_device(struct coresight_device *csdev) struct coresight_device *child; child = csdev->pdata->conns[i].child_dev;

• if (child && child->type == CORESIGHT_DEV_TYPE_HELPER)
  

• if (child && child->type == CORESIGHT_DEV_TYPE_HELPER) {
  

• 	if (!try_module_get(child->dev.parent->driver->owner))
  

• 		goto err;
  

• 	get_device(child->dev.parent);
  pm_runtime_get_sync(child->dev.parent);
  

• }
  

  }

This could then be : if (child && child->type == CORESIGHT_DEV_TYPE_HELPER) if (!coresight_get_ref(child)) goto err;

• if (!try_module_get(csdev->dev.parent->driver->owner))

• goto err;
  

• get_device(csdev->dev.parent); pm_runtime_get_sync(csdev->dev.parent);

if (coresight_get_ref(csdev)) return 0;

• 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)
  

• 	pm_runtime_put(child->dev.parent);
  

• 	put_device(child->dev.parent);
  

• 	module_put(child->dev.parent->driver->owner);
  

• }
  

And this could be :

if (child && child->type == CORESIGHT_DEV_TYPE_HELPER) coresight_put_ref(child);

• }
• return -ENODEV; }

/* @@ -663,12 +683,17 @@ static void coresight_drop_device(struct coresight_device *csdev) int i; pm_runtime_put(csdev->dev.parent);

• put_device(csdev->dev.parent);
• module_put(csdev->dev.parent->driver->owner);

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)
  

• if (child && child->type == CORESIGHT_DEV_TYPE_HELPER) {
  pm_runtime_put(child->dev.parent);
  

• 	put_device(child->dev.parent);
  

• 	module_put(child->dev.parent->driver->owner);
  

• }
  

coresight_put_ref(child);

} } @@ -687,7 +712,7 @@ 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;

@@ -721,7 +746,11 @@ static int _coresight_build_path(struct coresight_device *csdev, if (!node) return -ENOMEM;

• coresight_grab_device(csdev);

• ret = coresight_grab_device(csdev);
• if (ret) {

• kfree(node);
  

• return ret;
  

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

Cheers Suzuki