[PATCH v6 06/25] coresight: add try_get_module() in coresight_grab_device()

[Mike Leach]

On Fri, 31 Jul 2020 at 07:41, Tingwei Zhang <tingwei at 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.
> Use get_device()/put_device() to protect device data
> in the middle of active session.
>
> Signed-off-by: Tingwei Zhang <tingwei at codeaurora.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;
>
> @@ -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);
> +               }
>         }
> +       if (!try_module_get(csdev->dev.parent->driver->owner))
> +               goto err;
> +       get_device(csdev->dev.parent);
>         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);
> +                       put_device(child->dev.parent);
> +                       module_put(child->dev.parent->driver->owner);
> +               }
> +       }
> +       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);
>         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);
> +               }
>         }
>  }
>
> @@ -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);
>
> --
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> a Linux Foundation Collaborative Project
>

Tested by: Mike Leach <mike.leach at linaro.org>

--
Mike Leach
Principal Engineer, ARM Ltd.
Manchester Design Centre. UK