On Wed, 7 Aug 2019 04:34:24 +0000, Hayes Wang wrote: > Jakub Kicinski [mailto:jakub.kicinski@xxxxxxxxxxxxx] > > > static int rtl_stop_rx(struct r8152 *tp) > > > { > > > - int i; > > > + struct list_head *cursor, *next, tmp_list; > > > + unsigned long flags; > > > + > > > + INIT_LIST_HEAD(&tmp_list); > > > > > > - for (i = 0; i < RTL8152_MAX_RX; i++) > > > - usb_kill_urb(tp->rx_info[i].urb); > > > + /* The usb_kill_urb() couldn't be used in atomic. > > > + * Therefore, move the list of rx_info to a tmp one. > > > + * Then, list_for_each_safe could be used without > > > + * spin lock. > > > + */ > > > > Would you mind explaining in a little more detail why taking the > > entries from the list for a brief period of time is safe? > > Usually, it needs the spin lock before accessing the entry > of the list "tp->rx_info". However, for some reasons, > if we want to access the entry without spin lock, we > cloud move all entries to a local list temporally. Then, > we could make sure no other one could access the entries > included in the temporal local list. > > For this case, when I move all entries to a temporal > local list, no other one could access them. Therefore, > I could access the entries included in the temporal local > list without spin lock. I see, thanks for the explanation.
