I was reading through the ACPI spec, to see what was required to obtain
the IRQ routing table from AML. Continued reading... until I hit a
section talking about the ACPI global lock.
events/evxface.c:610:acpi_acquire_global_lock ->
events/evmisc.c:337:acpi_ev_acquire_global_lock ->
include/platform/acgcc.h:52:ACPI_ACQUIRE_GLOBAL_LOCK
My immediate objections are,
(a) acgcc.h is re-implementing spinlocks in a non-standard,
non-portable, and expensive way, and (b) this entire code path is
incredibly expensive.
But my fundamental objection is,
we are depending on vendors to get locking right in their ACPI tables.
And assume by some magic or design that said locking works with whatever
unrelated kernel locking is going on.
It is my initial belief that a smaller info query interface that can
parse useful ACPI would be more effective. For times like
suspend/resume where we would want to execute control methods, well,
there's always the disasm -> write-small-driver cycle. Who knows if
this is a realistics proposed solution. But it really scares me to
depend on vendors to get locking right.
We'll see what 2.5 will bring...
</soapbox>
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