Re: [PATCH 1/2] kvm: use modern cpumask primitives, no cpumask_ton stack

From: Avi Kivity
Date: Sun Dec 07 2008 - 11:14:20 EST

Avi Kivity wrote:
Rusty Russell wrote:
We're getting rid on on-stack cpumasks for large NR_CPUS.

1) Use cpumask_var_t and alloc_cpumask_var (a noop normally). Fallback
code is inefficient but never happens in practice.

Wow, code duplication from Rusty. Things must be bad.

Since we're in a get_cpu() here, how about a per_cpu static cpumask instead? I don't mind the inefficient fallback, just the duplication.

Btw, for the general case, instead of forcing everyone to duplicate, how about:

cpumask_var_t cpus;

with_cpumask(cpus) {
... code to populate cpus
} end_with_cpumask(cpus);

Where with_cpumask() allocates cpus, and uses a mutex + static fallback on failure.

May need a couple of variants (spinlock + GFP_NOWAIT, mutex with sleeping allocation).

error compiling committee.c: too many arguments to function

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