Re: [PATCH v4 06/20] coresight: add try_get_module() in coresight_grab_device()

Hi Tingwei,

On Thu, 23 Jul 2020 at 05:28, Tingwei Zhang tingwei@codeaurora.org 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.

Signed-off-by: Tingwei Zhang tingwei@codeaurora.org

drivers/hwtracing/coresight/coresight.c | 27 +++++++++++++++++++++---- 1 file changed, 23 insertions(+), 4 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight.c b/drivers/hwtracing/coresight/coresight.c index b7151c5f81b1..17bc76ea86ae 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;

@@ -648,10 +648,25 @@ 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;
                    pm_runtime_get_sync(child->dev.parent);
  

•           }
    }
  

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

•           goto err;
    pm_runtime_get_sync(csdev->dev.parent);
  

•   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);
  

•   }
  

•   return -ENODEV;
  

}

/* @@ -663,12 +678,15 @@ static void coresight_drop_device(struct coresight_device *csdev) int i;

    pm_runtime_put(csdev->dev.parent);

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

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

•           }
    }
  

}

@@ -721,7 +739,8 @@ static int _coresight_build_path(struct coresight_device *csdev, if (!node) return -ENOMEM;

•   coresight_grab_device(csdev);
  

•   if (coresight_grab_device(csdev))
  

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

-- The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project

The CTI devices are associated with other coresight components using csdev->ect_dev; These are not handled in the main linear trace path as these have a star topology interlinking all components. However, when a component has an associated ect_dev then is enabled at the same time as the other component is enabled.

So a module_get/put will be needed for this association to prevent the CTI being removed while a trace session is active. I suggest in coresight.c : coresight_control_assoc_ectdev()

Regards

Mike