On Wed, Jul 29, 2009 at 3:21 AM, Larry Finger<Larry.Finger@xxxxxxxxxxxx> wrote: > As shown in http://thread.gmane.org/gmane.linux.kernel.wireless.general/36497, > mac80211 has a bug that allows a call to the TX routine after the queues have > been stopped. This situation will only occur under extreme stress. Although > b43 does not crash when this condition occurs, it does generate a WARN_ON and > also logs a queue overrun message. This patch recognizes b43 is not at fault > and logs a message only when the most verbose debugging mode is enabled. In > the unlikely event that the queue is not stopped when the DMA queue becomes > full, then a warning is issued. > > During testing of this patch with one output stream running repeated tcpperf > writes and a second running a flood ping, this routine was entered with > the DMA ring stopped about once per hour. The condition where the DMA queue is > full but the ring has not been stopped has never been seen by me. > > Signed-off-by: Larry Finger <Larry.Finger@xxxxxxxxxxxx> > --- > > John, > > This patch is 2.6.32 material. > > Larry > --- > > Index: wireless-testing/drivers/net/wireless/b43/dma.c > =================================================================== > --- wireless-testing.orig/drivers/net/wireless/b43/dma.c > +++ wireless-testing/drivers/net/wireless/b43/dma.c > @@ -1334,13 +1334,23 @@ int b43_dma_tx(struct b43_wldev *dev, st > spin_lock_irqsave(&ring->lock, flags); > > B43_WARN_ON(!ring->tx); > - /* Check if the queue was stopped in mac80211, > - * but we got called nevertheless. > - * That would be a mac80211 bug. */ > - B43_WARN_ON(ring->stopped); > + > + if (unlikely(ring->stopped)) { > + /* We get here only because of a bug in mac80211. > + * Because of a race, one packet may be queued after > + * the queue is stopped, thus we got called when we shouldn't. > + * For now, just refuse the transmit. */ > + if (b43_debug(dev, B43_DBG_DMAVERBOSE)) > + b43err(dev->wl, "Packet after queue stopped\n"); > + err = -ENOSPC; > + goto out_unlock; > + } > > if (unlikely(free_slots(ring) < TX_SLOTS_PER_FRAME)) { > - b43warn(dev->wl, "DMA queue overflow\n"); > + /* If we get here, we have a real error with the queue > + * full, but queues not stopped. */ > + b43err(dev->wl, "DMA queue overflow\n"); > + WARN_ON(1); Is this really the best way to do this? Any reason why not have the WARN_ON in the if-condition? > err = -ENOSPC; > goto out_unlock; > } > -- > 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 > -- Vista: [V]iruses, [I]ntruders, [S]pyware, [T]rojans and [A]dware. :-) -- 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
