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Date:      Thu, 15 Nov 2012 10:39:35 -0700
From:      Ian Lepore <freebsd@damnhippie.dyndns.org>
To:        Adrian Chadd <adrian@freebsd.org>
Cc:        freebsd-hackers@freebsd.org, freebsd-arch@freebsd.org
Subject:   Re: [RFQ] make witness panic an option
Message-ID:  <1353001175.1217.153.camel@revolution.hippie.lan>
In-Reply-To: <CAJ-Vmo=i=Amo_QqHi4GnGie0Gc0YnK3XaRKjvBO-=SFboFYPmA@mail.gmail.com>
References:  <CAJ-Vmo=i=Amo_QqHi4GnGie0Gc0YnK3XaRKjvBO-=SFboFYPmA@mail.gmail.com>

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On Wed, 2012-11-14 at 22:15 -0800, Adrian Chadd wrote:
> Hi all,
> 
> When debugging and writing wireless drivers/stack code, I like to
> sprinkle lots of locking assertions everywhere. However, this does
> cause things to panic quite often during active development.
> 
> This patch (against stable/9) makes the actual panic itself
> configurable. It still prints the message regardless.
> 
> This has allowed me to sprinkle more locking assertions everywhere to
> investigate whether particular paths have been hit or not. I don't
> necessarily want those to panic the kernel.
> 
> I'd like everyone to consider this for FreeBSD-HEAD.
> 
> Thanks!

I strongly support this, because I'm tired of having to hack it in by
hand every time I need it.

You can't boot an arm platform right now (on freebsd 8, 9, or 10)
without a LOR very early in the boot.  Once you get past that, 2 or 3
device drivers I use panic way before we even get to mounting root.
Those panics can clearly be ignored, because we've been shipping
products for years based on this code.  (It's on my to-do list to fix
them, but more pressing problems are higher on the list.)

When a new problem crops up that isn't harmless, it totally sucks that I
can't just turn on witness without first hacking the code to make the
known problems non-panicky.

-- Ian





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