usbd_bulk_transfer returns 1 (USBD_IN_PROGRESS) ?!

[Seb]

Ok, I understood the problem.
But I didn't fix it with mutexes, I used semaphores instead.
I initialize a semaphore with a value equal to 1 and then, before the USB 
transfers, I do :
mtx_unlock(&Giant);
sema_wait(&sc->usb_tx_sema);
mtx_lock(&Giant);
And after the USB transfers :
sema_post(&sc->usb_tx_sema);
Is this OK ? Apparently it has solved the problem, the driver now sustains 
heavy network load :)
I wouln't like to use asynchronous transfers, they make the code hard to read 
and would require all users to recompile their kernels to install your USB 
driver...
Regards,
Sebastien