On Mon, Jan 19, 2015 at 6:48 PM, Hayes Wang <hayeswang@xxxxxxxxxxx> wrote: > David Miller [mailto:davem@xxxxxxxxxxxxx] >> Sent: Tuesday, January 20, 2015 5:14 AM > [...] >> >> - r8152_submit_rx(tp, agg, GFP_ATOMIC); >> >> + if (!ret) { >> >> + ret = r8152_submit_rx(tp, agg, GFP_ATOMIC); >> >> + } else { >> >> + urb->actual_length = 0; >> >> + list_add_tail(&agg->list, next); >> > >> > Do you need a spin_lock_irqsave(&tp->rx_lock, flags) around this? >> >> Indeed, and rtl_start_rx() seems to also access agg->list without >> proper locking. > > It is unnecessary because I deal with them in a local list_head. My steps are > 1. Move the whole list from tp->rx_done to local rx_queue. (with spin lock) > 2. dequeue/enqueue the lists in rx_queue. > 3. Move the lists in rx_queue to tp->rx_done if it is necessary. (spin lock) > For step 2, it wouldn't have race, because the list_head is local and no other > function would change it. Therefore, I don't think it needs the spin lock. Sorry guys, I think I made a mistake in my review and caused some confusion/grief. My mistake was getting the params to list_add_tail() backwards. It's list_add_tail(entry, head). I saw list_add_tail(&agg->list, next) and was fooled into thinking agg->list was the list getting appended with the entry 'next'. It's the opposite. Duh. So locking isn't needed because the list is indeed local. -scott -- 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
