backtrace() and the console log (was Re: cvs commit: src/sys/alpha...)

[Bruce Evans]

On Thu, 22 Jan 2004, Greg 'groggy' Lehey wrote:

> On Wednesday, 21 January 2004 at 16:40:46 +1100, Bruce Evans wrote:
> > On Tue, 20 Jan 2004, Nate Lawson wrote:
> >
> >> On Wed, 21 Jan 2004, Ian Dowse wrote:
> >>> I've been using the following patch for a while to get backtrace()
> >>> to output to the kernel message buffer. Sending all ddb output via
> >>> printf might be undesirable for some cases, but I guess having it
> >>> configurable with a `debug.ddb_use_printf' sysctl that defaults to
> >>> the old behaviour would be ok?
> >
> > It's undesireable in almost all cases, since it fills up the message
> > buffer with garbage.
>
> If it's "garbage", why are we ever producing it?  Currently I'm
> getting a lot of LORs which don't get reported anywhere.  I'd really
> like to catch this "garbage".

Because it is hard to debug when the debugger doesn't print any output.
In almost all cases, you don't want to record all the false trails that
you followed tracking down a problem, especially since any recording might
cycle more important records out of the message buffer before syslogd(8)
has a chance to run.

Bruce