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    SubjectRe: [PATCH 2/7] containers (V7): Cpusets hooked into containers
    On 3/7/07, Srivatsa Vaddagiri <> wrote:
    > On Mon, Feb 12, 2007 at 12:15:23AM -0800, wrote:
    > > - mutex_lock(&callback_mutex);
    > > - list_add(&cs->sibling, &cs->parent->children);
    > > + cont->cpuset = cs;
    > > + cs->container = cont;
    > > number_of_cpusets++;
    > > - mutex_unlock(&callback_mutex);
    > What's the rule to read/write number_of_cpusets? The earlier cpuset code was
    > incrementing/decrementing under callback_mutex, but now we aren't. How safe is
    > that?

    We're still inside manage_mutex, so we guarantee that no-one else is
    changing it.

    > The earlier cpuset code also was reading number_of_cpusets w/o the
    > callback_mutex held (atleast in cpuset_zone_allowed_softwall). Is that safe?

    Yes, I think so. Unless every memory allocator was to hold a lock for
    the duration of alloc_pages(), number_of_cpusets can theoretically be
    out of date by the time you're using it. But since the process could
    have allocated just before you created the first cpuset and moved it
    into that cpuset anywa, it's not really a race (and the consequences
    are inconsequential).

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      Last update: 2007-03-07 17:15    [W:0.024 / U:5.684 seconds]
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