[RFQ] make witness panic an option

[Pawel Jakub Dawidek]

On Sun, Nov 25, 2012 at 12:42:16PM +0000, Attilio Rao wrote:
> On Sun, Nov 25, 2012 at 12:39 PM, Pawel Jakub Dawidek <pjd at freebsd.org> wrote:
> > WITNESS is a development tool. We don't ship production kernels with
> > WITNESS even compiled in. What is more efficient use of developer time:
> > going through full reboot cycle every time or reading the warning from
> > console, unloading a module, fixing the bug and loading it again?
> >
> > And if this option is turned off by default what is the problem?
> 
> Yes, so, why do you write here?

I'm trying to understand why do you object. Until now the only concern
you have that I found is that you are afraid of it being abused. I don't
see how this can be abused if it is turned off by default. If someone
will commit a change that will turn it on by default, believe me, I'll
unleash hell personally.

As I said, WITNESS is development tool, a very handy one. This doesn't
mean we can't make it even more handy. It is there to help find bugs
faster, right? Adrian is proposing a change that will make it help to
find and fix bugs maybe even faster.

> Go ahead and fix BLESSED, make it the default, etc.

This is another story, but BLESSED is much less controversial to me.
It is turned off by default in assumption that all the code that runs in
our kernel is developed for FreeBSD, which is not true. For example ZFS
is, I think, the biggest locking consumer in our kernel (around 120
locks), which wasn't originally developed for FreeBSD and locking order
was verified using different tools. Now on FreeBSD it triggers massive
LOR warnings from WITNESS, eventhough those are not bugs. At some point
I verified many of them and they were all false-positives, so I simply
turned off WITNESS warnings for ZFS locks. Why? Because BLESSED is
turned off in fear of abuse, and this is turn is the cause of mentioned
hack in ZFS.

> I have enough of your (not referred to you particulary but to the
> people which contributed to this and other thread) to not be able to
> respect others opinion.
> As I said I cannot forbid you guys from doing anything, just go ahead,
> write the code and commit it, albeit completely bypassing other
> people's opinion.

I'm sorry, I wasn't aware that your opinions are set in stone. I hoped
that with some new arguments you may want to reconsider:)

-- 
Pawel Jakub Dawidek                       http://www.wheelsystems.com
FreeBSD committer                         http://www.FreeBSD.org
Am I Evil? Yes, I Am!                     http://tupytaj.pl
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