Re: [linux-usb-devel] Re: serious 2.6 bug in USB subsystem?

From: David Mosberger (davidm_at_napali.hpl.hp.com)
Date: 10/30/03

  • Next message: Theodore Ts'o: "Re: Things that Longhorn seems to be doing right" 
    Date:	Thu, 30 Oct 2003 12:15:19 -0800
To: David Brownell <david-b@pacbell.net>

    >>>>> On Thu, 30 Oct 2003 07:11:42 -0800, David Brownell <david-b@pacbell.net> said:

      David> David Mosberger wrote:

    >> On x86, there is no OOps, it just freezes. On ia64, I get a nice MCA
    >> and from that we can infer that a USB host controller read from
    >> address 0xf0000000 caused the problem but since this is asynchronous
    >> to the kernel's code path, the instruction pointer etc. in the MCA
    >> state dump isn't terribly helpful.

      David> Does that 0xf0000000 (on ia64) match any obvious address mapping
      David> of the null pointer -- like a dma mapping?

    Not really. AFAIK, 0xf0000000 is part of the PCI MMIO address space,
    but on the machines that I have access to, this particular address
    isn't assigned to any device:

            $ lspci -v|fgrep 'Memory at'
            Memory at 0000000080000000 (32-bit, prefetchable) [size=128M]
            Memory at 0000000088000000 (32-bit, non-prefetchable) [size=512K]
            Memory at 00000000d0023000 (32-bit, non-prefetchable) [size=4K]
            Memory at 00000000d0022000 (32-bit, non-prefetchable) [size=4K]
            Memory at 00000000d0021000 (32-bit, non-prefetchable) [size=256]
            Memory at 00000000d0020000 (32-bit, non-prefetchable) [size=4K]
            Memory at 00000000d0000000 (32-bit, non-prefetchable) [size=128K]
            Memory at 00000000e0200000 (32-bit, non-prefetchable) [size=4K]
            Memory at 00000000e0100000 (32-bit, non-prefetchable) [size=1M]

      David> I'm not sure that if the HID driver were to pass a null
      David> buffer pointer, it would be caught anywhere.

    OK, I'll try to find some time to trace the I/O MMU calls to see if
    something isn't kosher at that level. Is there a good way of getting
    a relatively high-level of tracing in the USB subsystem that would
    some me what's going on between the HID and the core USB level?

            --david
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