2010/4/7 Sujith <Sujith.Manoharan@xxxxxxxxxxx>: > Ming Lei wrote: >> 2010/4/6 Sujith <Sujith.Manoharan@xxxxxxxxxxx>: >> > Use a spin lock to prevent concurrent access >> > to variables dealing with RX stream mode handling. >> >> which variables are needed to be protected? >> >> It seems hif_dev->rx_transfer_len, hif_dev->remain_skb >> and hif_dev->rx_pkt_len are only accessed in ath9k_hif_usb_rx_stream, >> which is only called in hard irq(urb->complete) context and now is >> serialized strictly, so the protection is useless, isn't it? > > On a SMP machine, the RX callback can run on two CPUs, in this case, > appropriate protection is needed between the two hard-irq handlers. I am not sure if the same irq handler can run concurrently on different CPUs. Even though it is, ehci/uhci handler have done such protection, so it is not necessary to add such protection in the complete handler of usb interface driver. > >> > Currently, no protection is implemented - which >> > causes problems in RX. >> >> which problems? Could you describe them in detail? > > The RX stream position-hooks would get mangled up if two > IRQ handlers access them without any kind of protection. > This corrupts the stream data - causing data loss. > > Sujith > -- Lei Ming -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
