BBB freebsd-current backtrace. why?

[Warner Losh]

> On Mar 11, 2015, at 11:11 PM, Ian Lepore <ian at FreeBSD.org> wrote:
> 
> On Tue, 2015-03-10 at 21:09 -0700, jungle Boogie wrote:
>> Hi Jason,
>> On 10 March 2015 at 19:05, Jason Birch <jbirch at jbirch.net> wrote:
>>> 
>>> They're lock order reversals, as enabled by the WITNESS kernel option. You
>>> probably don't need to worry, but it's helpful to check if they've been
>>> reported and, if not, report them.
>>> 
>>> You might be running into this one:
>>> http://sources.zabbadoz.net/freebsd/lor/261.html
>>> 
>>> Quick Googling turns up these resources:
>>> 
>>> lock order reversals - what do they mean?:
>>> https://lists.freebsd.org/pipermail/freebsd-current/2003-December/016617.html
>>> Glossary of Kernel Options for Debugging:
>>> https://www.freebsd.org/doc/en/books/developers-handbook/kerneldebug-options.html
>>> FreeBSD LOR(lock order reversal)s seen and comments:
>>> http://sources.zabbadoz.net/freebsd/lor.html
>> 
>> Based on what Ian says, I hope these BT don't continue. Those threads
>> are very likely before the BBB was made...much less had freeBSD
>> running, so hopefully some progress has been made with freeBSD.
> 
> The point is that those LORs are harmless.  They were declared harmless
> by the gurus who understand them, years ago, and apparently just by
> issuing that proclamation, it's a closed subject and we all just have to
> live with the spewage.

Except that’s not entirely true. There are some that are known to be harmless,
but others that aren’t. Sadly, there’s no way to mark the harmless ones in
the source.

Some LoRs are harmless, others lead to deadlock.

Warner

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