On Tue, 13 Apr 2010, Sarah Sharp wrote: > Ok, I think I understand what happened. The xhci-streams branch you > were testing against was based against 2.6.32 (the original one that > came out, not any of the stable versions that followed). That kernel > didn't have David Vrabel's patch to make the URB scatter gather support > more generic (commit 4c1bd3d7a7d114dabd58f62f386ac4bfd268be1f), and thus > the USB mass storage driver didn't check bus->sg_tablesize. > > When you modified max_sectors, the mass storage driver would blindly > enqueue a scatter gather list with more entries than the xHCI driver > could handle. We never saw this issue before because the max_sectors > was always low. You didn't see this issue on the xhci-large-tx branch > because it's based on 2.6.34-rc2. > > I don't think we need to patch the stable kernel series, because it > won't have a driver that triggers this bug, and we won't allow new > drivers to go into the stable kernels. If I understand this correctly, it means that you don't have to worry about enlarging the rings on-the-fly. The number of outstanding scatterlist elements will always be limited by TRBS_PER_SEGEMENT. Is that correct? Alan Stern -- 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
