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SubjectRe: [DOC] Debugging early kernel hangs
On Fri, 22 Sep 2000, Keith Owens wrote:

> If a kernel hangs early in the boot process (before the console has
> been initialized) then printk is no use because you never see the
> output. There is a technique for using the video display to indicate
> boot progress so you can localize the problem. Reporting "my kernel
> hangs during boot at line nnn in routine xyz" is a lot better than "my
> kernel hangs during boot".
> The idea is to write characters direct to the video screen during
> booting using a macro called VIDEO_CHAR. This macro takes a character
> position and a single character value to be displayed. Use different
> positions on the screen for different levels of code and use different
> characters in one position to indicate which stage that level is up to.
> For example, with the patch below, the string EAC at hang indicates
> parse_options(), checksetup().

Why not just redirect printk() to output a string of characters one by one
using VIDEO_CHAR until the console subsystem is initialized. You can use a
statically defined int to keep track of what row & column you're on. There is
no need to be so cryptic about the readout.


Byron Stanoszek Ph: (330) 644-3059
Systems Programmer Fax: (330) 644-8110
Commercial Timesharing Inc. Email:

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