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    SubjectRe: possible migration bug with hotplug cpu
    On Thu, 2009-07-09 at 13:57 +0200, Lucas De Marchi wrote:
    > So, I found the problem.
    > These fields are currently not initialized upon fork. I noted that when I
    > updated to 2.6.31-rc2; commit 6c594c21fcb02c662f11c97be4d7d2b73060a205 was
    > merged into kernel by Ingo (not present yet in 2.6.30), but it only initializes
    > nr_migrations. Why the other fields are not initialized to 0? Even when there
    > are more processors, these fields may be wrong if not zeroed when a new task
    > is started. Below the fast way to fix it. This fixed the counters for me.

    Ah, awesome. I hadn't had time to look in detail yet. Thanks!

    > What do you think of creating a struct sched_statistics embedded into
    > sched_entity so we coudl memset it to zero all at once? All fields of
    > SCHED_STATS piece should be initialized, right?

    Sounds like a sane plan.

    One of the things I have wanted to do for a long time is to rename
    sched_entity to sched_fair_entity, and do something like:

    struct sched_entity {
    struct sched_common_entity common;

    union {
    struct sched_fair_entity fair;
    struct sched_rt_entity rt;

    I imagine we can add struct sched_statistics to the end of this as well.

    The reason I haven't come around to doing this is that it takes a bit of
    time to refactor the code and find all the common bits. So its been on
    my todo list like forever.

    Can I persuade you to look at this? :-)

    I'll queue the below, can I add:

    Signed-off-by: Lucas De Marchi <>


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