[coreboot] locking...

Carl-Daniel Hailfinger c-d.hailfinger.devel.2006 at gmx.net
Fri Jun 19 18:02:37 CEST 2009


as we move into the multicore world, messages get harder and harder to
read when they are interspersed byte-wise. I propose to add optional
locking to printk.

However, this locking has to work when some CPUs are in CAR and others
are in RAM. And that's the big problem.

AFAICS we can't simply use atomic normal memory acceses since the CPUs
in CAR won't see that. Atomic register modifications are not possible
across processors AFAICS.
The only idea I have is abusing some MMIO chipset/CPU space which is
usable as scratch space. In theory, that should work. But do CPUs or
chipsets have such MMIO areas?

Of course, I'm aware that locking (if possible at all) will be highly
CPU/chipset dependent, but even if we can make locking work on only a
subset of platforms, it is still a lot better than nothing.

Ideas? Utter rejection? Tell me.



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