On 2018-06-12 12:43:01 [-0400], Alan Stern wrote: > On Tue, 12 Jun 2018, Sebastian Andrzej Siewior wrote: > > > In the code path > > __usb_hcd_giveback_urb() > > -> wdm_in_callback() > > -> service_outstanding_interrupt() > > > > The function service_outstanding_interrupt() will unconditionally enable > > interrupts during unlock and invoke usb_submit_urb() with GFP_KERNEL. > > If the HCD completes in BH (like ehci does) then the context remains > > atomic due local_bh_disable() and enabling interrupts does not change > > this. > > > > Add an argument to service_outstanding_interrupt() which decides > > whether or not it is save to enable interrupts during unlocking and use > > GFP_KERNEL or not. > > Wouldn't it be easier just to use spin_lock_irqsave() and GFP_ATOMIC > all the time? That's what people normally do with code that can be > called in both process and interrupt contexts. service_outstanding_interrupt() does unlock + lock instead lock + unlock. If you want to have this "always" working (without the argument), we could do the false case: + spin_unlock(&desc->iuspin); + rv = usb_submit_urb(desc->response, GFP_ATOMIC); + spin_lock(&desc->iuspin); all the time. I wanted to preserve the GFP_KERNEL part which is probably used more often but fell that this is not needed I could drop that part. > Alan Stern Sebastian -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
