Date: Wed, 21 Jan 2004 11:15:48 -0500 From: John Baldwin <jhb@FreeBSD.org> To: Nate Lawson <nate@root.org>, "Greg 'groggy' Lehey" <grog@FreeBSD.org> Cc: cvs-all@FreeBSD.org Subject: Re: cvs commit: src/sys/alpha/alpha support.s src/sys/i386/i386 swtch.s src/sys/kern kern_shutdown.c src/sys/sys systm.h Message-ID: <200401211115.48851.jhb@FreeBSD.org> In-Reply-To: <20040120164435.I98793@root.org> References: <200401192127.i0JLRBL3041817@repoman.freebsd.org> <20040121004238.GP47639@wantadilla.lemis.com> <20040120164435.I98793@root.org>
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On Tuesday 20 January 2004 08:04 pm, Nate Lawson wrote:
> On Wed, 21 Jan 2004, Greg 'groggy' Lehey wrote:
> > On Tuesday, 20 January 2004 at 11:31:03 -0800, Nate Lawson wrote:
> > > * GDB over Ethernet
> >
> > We have GDB over firewire. Ethernet would be nice too, but firewire
> > actually does more. Take a look at gdb(4) (new man page).
>
> I'm glad to have this. More machines have ethernet than firewire ports
> though.
>
> > > We don't need file/line added to the panic message since panic
> > > messages are unambiguous.
> >
> > You still need to grep for them.
>
> There are basically two kinds of panics: assertions and page faults.
> Assertions, whether KASSERT or explicit checks/panic calls, give a unique,
> easily identified message ("foo driver: invalid mbuf length, %d"). If
> this is not obvious enough even without grep, then the panic message
> should be fixed. There is no difference between "vi +line file.c" and
> "vi file.c /msg", hence phk's commit is not useful in this case.
>
> Page faults are much harder to track down from the start. You find
> whether or not it was a NULL pointer, the curproc, and PC. So the next
> step is to have them recompile with options DDB or preferably -g and type
> "tr" at the DDB prompt. The changes to panic do not help this case at all
> since you get the file and line of the page fault handler.
>
> I would have gotten 100x more value from making options DDB the default in
> GENERIC (at least until we branch -stable) and having all page faults
> generate a backtrace. This is a 1 line change that would save hours, not
> minutes, of roundtrip email. Look at reports of panics in the
> freebsd-current@ archives and see how many result in a request for a
> backtrace.
DDB is on GENERIC. Just DDB_TRACE is not on.
--
John Baldwin <jhb@FreeBSD.org> <>< http://www.FreeBSD.org/~jhb/
"Power Users Use the Power to Serve" = http://www.FreeBSD.org
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