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    SubjectRe: [bug ?] do_get_mempolicy()
    On Thu, 2008-07-03 at 16:44 -0400, John Blackwood wrote:
    > Hi Lee,

    John: I'm just getting back from a long weekend and I'm wading through
    a big e-mail back log. I'll take a look at this when I get to the end
    of my inbox. I/m probably responsible for that line. I recall thinking
    that get_mempolicy() should return the policy that one would pass back
    in to achieve the same effect. But, I blew it.

    > I'm having unexpected results with get_mempolicy(2) in 2.6.26, and
    > I am hoping that you can either agree with me, or maybe comment on my
    > misconceptions.
    > When I have a task with no special task mempolicy (the default mempolicy),
    > when I call get_mempolicy(2), it returns a policy value of 2 (MPOL_BIND)
    > with a NULL nodemask.
    > I believe that this is because of the code in do_get_mempolicy() that does:
    > *policy |= pol->flags;
    > in the else case when flags do not contain MPOL_F_NODE.

    I think that need to mask off the internal flags, and shift the
    remaining ones up to the correct location. I'll send a patch, if no one
    beats me to it.

    > I guess I don't understand why we are ORing in the pol->flags into the
    > *policy value. For example, when this is for the default_policy, the
    > MPOL_F_LOCAL flag (which has a value of 2) gets stuffed into the *policy
    > location, and a get_mempolicy(2) caller sees this as the MPOL_BIND
    > mempolicy.
    > Maybe the "*policy |= pol->flags;" line should be removed ?
    > That is, maybe it was valid at some point, but subsequent changes
    > make this line of code no longer valid ?
    > Sorry if I'm out-to-lunch here...

    No, doesn't appear that way..

    > Thanks very much for you time and considerations on this issue.

    thanks for reporting it.


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