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    SubjectRe: [Patch 00/11] Hardware Breakpoint interfaces
    On Fri, Apr 24, 2009 at 10:16:07AM -0400, Alan Stern wrote:
    > On Fri, 24 Apr 2009, K.Prasad wrote:
    >
    > > The arch_update_kernel_hw_breakpoints() was designed to work like this -
    > > it updates all registers beginning 'hbp_kernel_pos' to (HB_NUM - 1) with
    > > the values stored in hbp_kernel[] array.
    > >
    > > When inserting a new breakpoint, hbp_kernel_pos is decremented *before*
    > > invoking arch_update_kernel_hw_breakpoints() so that the new value is
    > > also written onto the physical debug register.
    > >
    > > On removal, 'hbp_kernel_pos' is incremented *after*
    > > arch_update_kernel_hw_breakpoints() so that the physical debug registers
    > > i.e. both DR7 and DR<pos> are updated with the changes post removal and
    > > compaction. I'm ready to make changes but don't see where the code
    > > actually goes wrong. Can you explain that?
    >
    > I'm sorry; I misread the code in arch_update_kernel_hw_breakpoints().
    > It isn't actually wrong, and you are correct to increment
    > hbp_kernel_pos where you do. Your code is different from my original
    > version, which would update all the debug registers at once instead of
    > doing the kernel and userspace breakpoints separately -- that's what
    > confused me.
    >
    > There is one change you could make to improve the routine, however. In
    > arch_update_kernel_hw_breakpoints(), the line
    >
    > kdr7 &= ~kdr7_masks[hbp_kernel_pos];
    >
    > really should be
    >
    > kdr7 = 0;
    >
    > since kdr7 never contains anything other than kernel breakpoint
    > settings. (You could update the comment in the preceding line as
    > well.)
    >
    > Alan Stern

    Sure, I'd make that change (in the subsequent iteration) - it's much simpler.

    Do you think that the patchset is now in a form that can be submitted
    for upstream (-tip tree) acceptance?

    Thanks,
    K.Prasad



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