Re: [PATCH 3/4] cpuset: Fix unchecked calls to NODEMASK_ALLOC()

[Paul Menage]

On Thu, Feb 17, 2011 at 2:46 PM, Andrew Morton
<akpm@xxxxxxxxxxxxxxxxxxxx> wrote:
> On Thu, 17 Feb 2011 09:50:09 +0800
> Li Zefan <lizf@xxxxxxxxxxxxxx> wrote:
>
>> +/*
>> + * In functions that can't propogate errno to users, to avoid declaring a
>> + * nodemask_t variable, and avoid using NODEMASK_ALLOC that can return
>> + * -ENOMEM, we use this global cpuset_mems.
>> + *
>> + * It should be used with cgroup_lock held.
>
> I'll do s/should/must/ - that would be a nasty bug.
>
> I'd be more comfortable about the maintainability of this optimisation
> if we had
>
>        WARN_ON(!cgroup_is_locked());
>
> at each site.
>

Agreed - that was my first thought on reading the patch. How about:

static nodemask_t *cpuset_static_nodemask() {
  static nodemask_t nodemask;
  WARN_ON(!cgroup_is_locked());
  return &nodemask;
}

and then just call cpuset_static_nodemask() in the various locations
being patched?

Paul
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