Printing from kernel

[Greg 'groggy' Lehey]

On Thursday,  7 October 2004 at  0:31:33 +0400, Roman Kurakin wrote:
> Hi,
>
> 	I have some problems with printing from kernel.
> At first I think that my problems was cause I use printf,
> but changed all of them to log cause it safe to use from
> interrupt handlers. The situation become better but I still
> observe system lockup in case I output some debug information
> from my driver.

About the only thing I can think is that you're doing this in some
area where it's unsafe to print, probably holding a lock that's needed
in the print routines.

> 	Also I have some problems with system console via com
> port. Instead of messages from kernel I see the first letter
> of the month name.
>
> 	Could anybody comment my observation?

Without more detail, it's impossible to help.

> Does anybody saw anything like this?

No.  printf() is widely used in the kernel.

> 	Oh, I forget to say I observe that with both Current
> and Releng5, SMP. Also I can't trigger NMI so I can't see the
> point of lockup.

Take a look at your code and check what locks you're holding.  Also,
if this is only for debugging, you should be using the kernel
debugger.

Greg
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