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    SubjectRe: [Bug 10489] Kprobe smoke test lockdep warning
    Peter Zijlstra wrote:
    > On Tue, 2008-04-22 at 15:09 +0200, Peter Zijlstra wrote:
    >> On Mon, 2008-04-21 at 18:54 -0400, Masami Hiramatsu wrote:
    >>> Thank you for reporting.
    >>>
    >>> Actually, kprobes tries to fixup thread's flags in post_kprobe_handler
    >>> (which is called from kprobe_exceptions_notify) by
    >>> trace_hardirqs_fixup_flags(pt_regs->flags). However, even the irq flag
    >>> is set in pt_regs->flags, true hardirq is still off until returning
    >>> from do_debug. Thus, lockdep assumes that hardirq is off without annotation.
    >
    > Ah, can you clarrify? pt_regs->flags will only be set when returning to
    > the original trap site? in that case we should not need a lockdep
    > annotation I guess, unless its allowed and exptected for the int3 site
    > to change IRQ state.

    As far as I took a look at the lockdep, your suggestion is correct.
    post_kprobe_handler should not set a lockdep annotation, because
    processor's IF is not changed yet in that time.

    Thanks,

    --
    Masami Hiramatsu

    Software Engineer
    Hitachi Computer Products (America) Inc.
    Software Solutions Division

    e-mail: mhiramat@redhat.com



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