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SMP alternatives
SMP alternatives
Posted Dec 15, 2005 18:39 UTC (Thu) by Ross (subscriber, #4065)In reply to: SMP alternatives by kpfleming
Parent article: SMP alternatives
That's not how I read it.
"The main use of SMP alternatives in his patch is with spinlock operations; spinlocks can be patched in or edited out, as dictated by the configuration of the system at boot time."
It sounds like spinlocks will be turned into noops. This may be ok when going SMP->UP, but maybe not the other direction, and I wonder what kind of lock state would be retained when going SMP->UP->SMP...
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SMP alternatives
Posted Dec 15, 2005 18:59 UTC (Thu) by im14u2c (subscriber, #5246) [Link]
To enable hotplug SMP -> UP -> SMP, you'd definitely need to retain spinlocks, or at least put a lightweight "take lock" instruction there as opposed to the full spin. Fully NOPping spinlocks out would be a disaster, as you note.
Elsewhere, though, you could nuke/replace LOCK prefixes as needed.