Witness patch

[Don Lewis]

On 15 Sep, John Baldwin wrote:
> On Friday 02 September 2005 05:37 pm, Don Lewis wrote:
>> On  2 Sep, John Baldwin wrote:
>> > On Thursday 01 September 2005 11:52 pm, Don Lewis wrote:

>> >> I think it would make sense to print different messages for the
>> >> different trigger conditions.
>> >
>> > Hmm, I guess I view them as all just being reversals, and that we have
>> > some implicit orders that go something like this:
>> >
>> > sleepable locks --> Giant --> non-sleepable locks --> spin locks
>>
>> Attempting to lock one one of the other lock types while holding a spin
>> lock already prints a unique message and results in a panic. Identifying
>> the other cases of incorrect lock type ordering with a unique warning
>> message eliminates the need to grovel through the source code just to
>> find the types of the locks, and it indicates that looking at the output
>> of "show witness" is not needed.
> 
> Ok.  I'll still list the reversal (so you know which locks are involved) but 
> will tailor the first line to include the implicit rule in parens if the 
> reversal is the result of an implicit rule.

Sounds perfect to me.