On Wed, Jul 22, 2020 at 11:49:48AM +0100, Suzuki K Poulose wrote:

Hi Tingwei,

On 07/17/2020 06:45 AM, Tingwei Zhang wrote:

quoted

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.

Is this really sufficient ? AFAIU, a device could be removed, but the
module may still be alive due to the refcount on the module. This
could imply that we have stale pointers in the _path_, which could
lead to corruption elsewhere. Should we do a get/put_device() instead ?

Remember there are two separate things here, code and data.  There are
two different reference counts for them, do not confuse the two.

get/put is needed when you have a reference to the data, module stuff is
when you are calling into code.

But note that you do not always need to grab a reference count to the
module, as long as the module can properly tear the data down when it is
asked to be removed.  Look at networking drivers as a great example of
that.

thanks,

greg k-h

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