RE: [2.6.25-rc5-mm1][regression] ia64: hackbench doesn't finish>12 hour

[Luck, Tony]

> Which makes me wonder, why did you ever use a semaphore here? Looking at
> the code its a straight forward mutex. And when you would have used a
> mutex lockdep would have warned about this.

The functionality that we are trying to add is to allow up to N
simultaneous processors to execute the critical region.  On current
processors/platforms N=1 so a spinlock or mutex would be fine, but
there will be platforms for which N is a small integer greater than
one.  Semaphore initialized to N looked to be the ideal primitive
for this (until Motohiro-san ran the test case that showed the path
where we call this code with a spinlock held).

Next question is whether it is reasonable to get to this code
while holding a spinlock.  Isn't this a problem for architectures
that need to use cross-processor interrupts to do a global TLB
shootdown?

-Tony
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