Hi Alan,
On 10/26/2021 1:57 PM, Alan Stern wrote:
> On Tue, Oct 26, 2021 at 12:40:04PM -0700, Wesley Cheng wrote:
>> Hi Alan,
>>
>> On 10/26/2021 7:41 AM, Alan Stern wrote:
>>> On Mon, Oct 25, 2021 at 05:44:56PM -0700, Wesley Cheng wrote:
>>>> From: Wesley Cheng <wcheng@xxxxxxxxxxxxxx>
>>>>
>>>> When receiving a disconnect event from the UDC, the mass storage
>>>> function driver currently runs the handle_exception() routine
>>>> asynchronously. For UDCs that support runtime PM, there is a
>>>> possibility the UDC is already suspended by the time the
>>>> do_set_interface() is executed. This can lead to HW register access
>>>> while the UDC is already suspended.
>>>>
>>>> Signed-off-by: Wesley Cheng <wcheng@xxxxxxxxxxxxxx>
>>>> ---
>>>> drivers/usb/gadget/function/f_mass_storage.c | 10 ++++++++++
>>>> 1 file changed, 10 insertions(+)
>>>>
>>>> diff --git a/drivers/usb/gadget/function/f_mass_storage.c b/drivers/usb/gadget/function/f_mass_storage.c
>>>> index 3cabf7692ee1..752439690fda 100644
>>>> --- a/drivers/usb/gadget/function/f_mass_storage.c
>>>> +++ b/drivers/usb/gadget/function/f_mass_storage.c
>>>> @@ -2342,6 +2342,16 @@ static void fsg_disable(struct usb_function *f)
>>>> {
>>>> struct fsg_dev *fsg = fsg_from_func(f);
>>>>
>>>> + /* Disable the endpoints */
>>>> + if (fsg->bulk_in_enabled) {
>>>> + usb_ep_disable(fsg->bulk_in);
>>>
>>> According to the kerneldoc, this routine must be called in process
>>> context.
>>>
>>>> + fsg->bulk_in_enabled = 0;
>>>> + }
>>>> + if (fsg->bulk_out_enabled) {
>>>> + usb_ep_disable(fsg->bulk_out);
>>>> + fsg->bulk_out_enabled = 0;
>>>> + }
>>>> +
>>>> __raise_exception(fsg->common, FSG_STATE_CONFIG_CHANGE, NULL);
>>>> }
>>>
>>> Looks like you'll have to find a different way to avoid the problem.
>>> For example, if an exception is pending then you might prevent the
>>> gadget from going into runtime suspend until the exception has been
>>> handled.
>>>
>> Thanks for the suggestion. I noticed that a lot of other FDs currently
>> call usb_ep_disable() in the disable/disconnect path as well. Actually,
>> f_mass_storage seems to be the only one that doesn't do so. Maybe we
>> should change the kerneldoc :)
>
> You're right; I don't see any real reason why the usb_ep_{en,dis}able
> routines can't run in an atomic context. So if you to make this change
> to f_mass_storage, you should first submit a patch changing the
> kerneldoc.
>
Sure, will do that and include it in the next rev.
Thanks
Wesley Cheng
