[lkml]   [2008]   [Oct]   [22]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
    SubjectRe: [PATCH 04/11] ftrace: comment arch ftrace code

    On Wed, 22 Oct 2008, Andrew Morton wrote:
    > I dunno.
    > __copy_to_user_inatomic() is for "copying memory from userspace while
    > in an atomic context".
    > But what you're doing here is "modifying some kernel text which might
    > generate a fault". It seems somewhat interface-abusive to use a
    > userspace access function for that just because it happens right now to
    > do the right thing.
    > I'd suggest that for clarity and for future-safety, you create some new
    > interface function which does that thing. Right now it can be a simple
    > wrapper around __copy_from_user_inatomic().
    > <looks>
    > oh, someone added one - probe_kernel_write(). Why not use that?

    I didn't know about that code. That is what I want.

    -- Steve

    > <wonders why he doesn't know what's going on any more>
    > Also, I hope that the above code is called from within a
    > pagefault_disable()d region? Or are relying upon some magical
    > side-effect of something which happens to do the same thing as
    > pagefault_disable()? IOW: by what means does the above code ensure
    > that do_page_fault() will see in_atomic()==true?

    This code is called from kstop_machine, or simply has interrupts disabled.

    -- Steve

     \ /
      Last update: 2008-10-22 21:19    [W:0.024 / U:1.400 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site