[PATCH v4 06/20] coresight: add try_get_module() in coresight_grab_device()
Greg Kroah-Hartman
gregkh at linuxfoundation.org
Thu Jul 23 07:07:07 EDT 2020
On Thu, Jul 23, 2020 at 12:27:48PM +0800, 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.
Are you sure this works? Why is it needed at all? Why not just tear
down the children properly when a module is removed so that you don't
need this at all?
>
> Signed-off-by: Tingwei Zhang <tingwei at 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))
Why the child's parent? Why not the child itself?
> + goto err;
What about the error given to you here? Why throw that away?
> pm_runtime_get_sync(child->dev.parent);
> + }
> }
> + if (!try_module_get(csdev->dev.parent->driver->owner))
> + goto err;
You don't reduce the child's parent's driver owner module reference
here?
Ugh, that's a horid sentence :(
> 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;
Why not return the error given to you?
thanks,
greg k-h
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