RE: [GIT PULL] scheduler fixes

Yuhong Bao
2009-10-02T16:40:50Z

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> [ If I recall correctly=2C cmpxchg8b support detection was something that
> was totally messed up in WNT=2C and I have this memory of TMTA _not_
> claiming to support CX8 in the cpuid bits=2C but happily supporting the
> instruction itself - because otherwise WNT would blue-screen on boot or
> something silly like that.
Yep=2C Geoff Chappell describe this bug excellently:http://www.geoffchappel=
l.com/viewer.htm?doc=3Dstudies/windows/km/cpu/cx8.htm
> As a result=2C the patch below only adds CMPXCHG8B for the obvious Intel
> CPU's=2C not for others. There was something really messy about cmpxchg8b
> and clone CPU's=2C but I'm not 100% sure about the details=2C so take thi=
s
> patch with a pinch of salt=2C and some thinking ]
Basically=2C pre-SP4 NT 4 would crash if the CX8 bit was set in CPUID and v=
endor was not GenuineIntel=2C AuthenticAMD=2C or CyrixInstead due to a bug =
in the CPU detection=2C XP had to workaround it too when it began requiring=
CX8.
Yuhong bao =0A=
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