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    SubjectRe: [PATCH] hwmon: coretemp: fix oops on cpu unplug
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    On Mon, 2012-04-30 at 12:19 -0400, Kirill A. Shutemov wrote:
    > On Mon, Apr 30, 2012 at 08:28:10AM -0700, Guenter Roeck wrote:
    > > Hi,
    > >
    > > good catch. Couple of problems, though.
    > >
    > > First, what number of cores are we talking about ? We should probably
    > > increase NUM_REAL_CORES as well. Long term, we should get rid of the
    > > dependency to prevent that problem from happening again, but that is a
    > > different issue.
    >
    > It triggered by another bug. Cores on my 10-core processor have ids 0, 1,
    > 2, 8, 9, 16, 17, 18, 24, 25. :-/
    > No need to change NUM_REAL_CORES at the moment.
    >
    The problem, though, is that core_data[] is indexed by the core ID. So,
    NUM_REAL_CORES is a bit misleading. It should probably be named
    NUM_CORE_ID or something similar.

    > > Second, we'll need the same code in get_core_online(). Otherwise the
    > > platform device can be created for the new core (if the core is
    > > re-enabled) but will never be deleted.
    >
    > It has already handled in create_core_data().
    >
    ... which is called from coretemp_add_core(), which does not return an
    error. Besides, it is called after the call to coretemp_device_add().

    As a result, the platform device for the unsupported core(s) will be
    created, even if the core is not supported. I just don't think that is a
    good idea.

    Besides, if you'd have the check in get_core_online(), you would not
    even hit the problem in put_core_offline(), since the platform device
    would not exist and the function would bail out because of that.

    Thanks,
    Guenter




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