PERFORCE change 108878 for review

[Scott Long]

John Baldwin wrote:
> On Thursday 02 November 2006 06:22, Hans Petter Selasky wrote:
> 
>>On Wednesday 01 November 2006 16:47, John Baldwin wrote:
>>
>>>On Tuesday 31 October 2006 20:12, Scott Long wrote:
>>>
>>>>http://perforce.freebsd.org/chv.cgi?CH=108878
>>>>
>>>>Change 108878 by scottl at scottl-x64 on 2006/11/01 01:11:30
>>>>
>>>> For some wonderful reason, you cannot pass &Giant to msleep.  Work
>>>> around that in a crude fashion.  Also add some more assertions.
>>>
>>>Ah, yes, that would be most unhappy.  I guess mostly the idea is that Giant
>>>should be rather implicit and explicitly using Giant for an object lock is
>>>discouraged.  I'm not sure that is what you are doing though.  I think
>>>maybe you are borrowing Giant that's already held?
>>
>>I use this patch:
>>
>>/* preliminary fix for a bug in msleep on FreeBSD, 
>> * which cannot sleep with Giant:
>> */
>>#define msleep(i,m,p,w,t) msleep(i,(((m) == &Giant) ? NULL : (m)),p,w,t)
>>
>>Really this issue should be fixed. It happens just because GIANT_DROP is done 
>>too early in "msleep()".
> 
> 
> Giant is special in msleep() and friends to make sure it is first in the
> lock order, but unlock doesn't matter for lock order, and actually, the
> current order is less intuitive.  I think it's the way it is now because we
> inherited it from BSD/OS.  Also in theory old code under Giant should be
> using tsleep() and not msleep() anyway.  It actually won't hurt to move
> DROP_GIANT later though.
> 
> How about this:
> 

This won't work for what I'm using it for.  It's not a big deal, though.

Scott