Re: [PATCH 2/4] ia64: allocate percpu area for cpu0 like percpuareas for other cpus

[Christoph Lameter]

On Wed, 23 Sep 2009, Tejun Heo wrote:

> On ia64, the first chunk is fixed at PERCPU_PAGE_SIZE.  It's something
> hardwired into the page fault logic and the linker script.  Build will
> fail if the static + reserved area goes over PERCPU_PAGE_SIZE and in
> that case ia64 will need to update the special case page fault logic
> and increase PERCPU_PAGE_SIZE.  The area reserved above is interim
> per-cpu area for cpu0 which is used between head.S and proper percpu
> area setup and will be ditched once initialization is complete.

You did not answer my question.

The local percpu variables are accessed via a static per cpu
virtual mapping. You cannot place per cpu variables outside of that
virtual address range of PERCPU_PAGE_SIZE.

What happens if the percpu allocator allocates more data than available in
the reserved area?

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