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    SubjectRe: frequent lockups in 3.18rc4
    On Sun, Dec 14, 2014 at 09:47:26PM -0800, Linus Torvalds wrote:
    > and "save_xstate_sig+0x81" shows up on all stacks, although only on
    > CPU1 does it show up as a "guaranteed" part of the stack chain (ie it
    > matches frame pointer data too). CPU1 also has that __clear_user show
    > up (which is called from save_xstate_sig), but not other CPU's. CPU2
    > and CPU3 have "save_xstate_sig+0x98" in addition to that +0x81 thing.
    >
    > My guess is that "save_xstate_sig+0x81" is the instruction after the
    > __clear_user call, and that CPU1 took the fault in __clear_user(),
    > while CPU2 and CPU3 took the fault at "save_xstate_sig+0x98" instead,
    > which I'd guess is the
    >
    > xsave64 (%rdi)

    Err, maybe a wild guess, but could XSAVE be encountering some problems,
    like store ordering violations or somesuch?

    Quick search shows

    "AZ72. Store Ordering Violation When Using XSAVE"

    here http://download.intel.com/design/mobile/specupdt/320121.pdf which
    talks about SSE context stores happening out of order. Now, there are a
    lot of IFs like does Dave's machine even have the erratum and even if,
    would that erratum cause some sort of a livelock leading to the kernel
    lockups and so on and so on...

    It might be worth to rule out though.

    --
    Regards/Gruss,
    Boris.

    Sent from a fat crate under my desk. Formatting is fine.
    --


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