Re: USB audio w/ "D" state

[Gabriel Paubert]

On Wed, 5 Dec 2001, Albert D. Cahalan wrote:

>
> I did "cat /bin/sh >> /dev/audio" and hit ^C to stop the noise.
> The "cat" process gets stuck in "D" state with the WCHAN indicating
> that the process is stuck 1/3 the way through the usbout_stop()
> function.
>
> hardware:  Mac Cube and the normal spherical speakers
> kernel:    plain 2.4.16 from www.kernel.org
> compiler:  gcc version 2.95.4 20011006 (Debian prerelease)
>
> In case PPC assembly is useful to somebody, I've marked the instruction
> where the process gets stuck. The surrounding "bl" instructions look
> like infinite loops to me, but maybe I'm reading this wrong. The assembly
> is from:   objdump -dl --start-address=0x1728 audio.o

Please add --reloc to this kind of dump, it makes the code much easier to
follow in case you hit a compiler bug (this happens). Or directly
disassemble vmlinux if it's not a module.

[snipped]
>     1790:       38 60 00 01     li      r3,1
>     1794:       48 00 00 01     bl      1794 <usbout_stop+0x6c>
                     ^^^^^^^^
these bytes (and the 2 LSB  of the first byte) will be modified by the
linker or module loader.

> --> 1798:       7f a3 eb 78     mr      r3,r29
>     179c:       48 00 00 01     bl      179c <usbout_stop+0x74>
>     17a0:       48 00 00 01     bl      17a0 <usbout_stop+0x78>

	Regards,
	Gabriel.