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Subject[PATCH 0/3] smp: reduce stack requirements for smp_call_function_mask

* Cleanup cpumask_t usages in smp_call_function_mask function chain
to prevent stack overflow problem when NR_CPUS=4096.

* Reduce the number of passed cpumask_t variables in the following
call chain for x86_64:

smp_call_function_mask -->
arch_send_call_function_ipi->
smp_ops.send_call_func_ipi -->
genapic->send_IPI_mask

Since the smp_call_function_mask() is an EXPORTED function, we
cannot change it's calling interface for a patch to 2.6.27.

The smp_ops.send_call_func_ipi interface is internal only and
has two arch provided functions:

arch/x86/kernel/smp.c: .send_call_func_ipi = native_send_call_func_ipi
arch/x86/xen/smp.c: .send_call_func_ipi = xen_smp_send_call_function_ipi
arch/x86/mach-voyager/voyager_smp.c: (uses native_send_call_func_ipi)

Therefore modifying the internal interface to use a cpumask_t pointer
is straight-forward.

The changes to genapic are much more extensive and are affected by the
recent additions of the x2apic modes, so they will be done for 2.6.28 only.

Based on 2.6.27-rc5-git6.

Applies to linux-2.6.tip/master (with FUZZ).

Signed-off-by: Mike Travis <travis@sgi.com>
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