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    SubjectRe: [PATCH 3/4] cpuset: Fix unchecked calls to NODEMASK_ALLOC()
    On Thu, Feb 17, 2011 at 2:46 PM, Andrew Morton
    <akpm@linux-foundation.org> wrote:
    > On Thu, 17 Feb 2011 09:50:09 +0800
    > Li Zefan <lizf@cn.fujitsu.com> 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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