Date: Wed, 21 Jan 2004 17:50:14 -0800 (PST) From: Nate Lawson <nate@root.org> To: Bruce Evans <bde@zeta.org.au> Cc: cvs-all@FreeBSD.org Subject: Re: backtrace() and the console log (was Re: cvs commit: src/sys/alpha...) Message-ID: <20040121174709.W5097@root.org> In-Reply-To: <20040122123454.V10548@gamplex.bde.org> References: <200401210148.aa95501@salmon.maths.tcd.ie> <20040120203001.B99547@root.org> <20040120144505.ccsc4kog4c88sgww@www.sweetdreamsracing.biz> <20040121235215.GV86671@wantadilla.lemis.com> <20040122123454.V10548@gamplex.bde.org>
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On Thu, 22 Jan 2004, Bruce Evans wrote: > 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. And...... cut! We're right back at the part where Ian says "hey, here's a patch" and then I say "hey, here's how to only dump non-DDB data to the message buffer" and then Bruce says "ok by me". Now we skip to the part where Ian commits it. -Nate (Oh, and I forgot the epilogue where the panic line numbers disappear because the backtrace is more useful. :)
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