On Thu, Oct 06, 2016 at 10:49:21AM +0200, Imre Vadasz wrote:
> Hi,
> This patch improves the error handling iwm_rx_addbuf(), specifically in
> out-of-memory and mbuf exhaustion cases.
>
> Keep an additional/spare bus_dmamap_t object around to make error handling
> for bus_dmamap_load_mbuf() failures easier in iwm_rx_addbuf().
> This seems like an easy way to avoid having weird panic() cases in the code
> (like in iwn, which then tries to bus_dmamap_load_mbuf() the old mbuf and
> panics when that fails).
>
> Move mbuf modifications that are needed before calling ieee80211_input()
> in iwm_rx_rx_mpdu() to below the iwm_rx_addbuf call. Otherwise we can end
> up with a broken mbuf in the rx ring when iwm_rx_rx_mpdu() aborts.
If memory is so tight that this panic triggers is it reasonable to
even try to recover? I honestly don't know.
This problem exists in many drivers.
Are we going to add a spare map to all of them?
$ egrep -i 'panic.*rx.*buf' pci/*c ic/*c
pci/if_ipw.c: panic("%s: could not load old rx mbuf",
pci/if_iwi.c: panic("%s: could not load old rx mbuf",
pci/if_iwm.c: panic("iwm: could not load RX mbuf");
pci/if_iwn.c: panic("%s: could not load old RX mbuf",
pci/if_ix.c: panic("%s: ixgbe_rxeof: NULL mbuf in slot %d "
pci/if_nfe.c: panic("%s: could not load old rx mbuf",
pci/if_pcn.c: panic("pcn_add_rxbuf");
pci/if_rtwn.c: panic("%s: could not load old RX mbuf",
pci/if_stge.c: panic("stge_add_rxbuf"); /* XXX */
pci/if_vio.c: panic("enqueue_prep for rx buffers: %d", r);
pci/if_wpi.c: panic("%s: could not load old RX mbuf",
ic/aic6915.c: panic("sf_add_rxbuf"); /* XXX */
ic/atw.c: panic("atw_add_rxbuf"); /* XXX */
ic/dwc_gmac.c: panic("%s: could not load old rx mbuf",
ic/gem.c: panic("gem_add_rxbuf"); /* XXX */
ic/malo.c: panic("%s: could not load old rx mbuf",
ic/rt2560.c: panic("%s: could not load old rx mbuf",
ic/rt2661.c: panic("%s: could not load old rx mbuf",
ic/rt2860.c: panic("%s: could not load old rx mbuf",
ic/smc83c170.c: panic("epic_add_rxbuf"); /* XXX */
