powerpc: Make the irq reverse mapping radix tree lockless

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The radix trees used by interrupt controllers for their irq reverse
mapping (currently only the XICS found on pSeries) have a complex
locking scheme dating back to before the advent of the lockless radix
tree.

This takes advantage of the lockless radix tree and of the fact that
the items of the tree are pointers to a static array (irq_map)
elements which can never go under us to simplify the locking.

Concurrency between readers and writers is handled by the intrinsic
properties of the lockless radix tree.  Concurrency between writers is
handled with a global mutex.

Signed-off-by: Sebastien Dugue <sebastien.dugue@bull.net>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Paul Mackerras <paulus@samba.org>

...

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Sebastien Dugue 2008-09-04 22:37:08 +10:00 • committed by Paul Mackerras

parent 967e012ef3

commit 150c6c8fec

1 changed files with 11 additions and 65 deletions

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arch/powerpc/kernel/irq.c

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