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    SubjectRe: [patch 1/8] Kprobes - do not use kprobes mutex in arch code
    * Christoph Hellwig ( wrote:
    > On Fri, Jul 13, 2007 at 09:21:34PM -0400, Mathieu Desnoyers wrote:
    > > Remove the kprobes mutex from kprobes.h, since it does not belong there. Also
    > > remove all use of this mutex in the architecture specific code, replacing it by
    > > a proper mutex lock/unlock in the architecture agnostic code.
    > This is not very nice for avr32/sparc64 which have a noop arch_remove_kprobe
    > and now need to take a mutex to do nothing. Maybe you can find a nice
    > way to avoid that?
    > Except for this issue making kprobes_mutex static to kprobes.c sounds like
    > a good improvement.

    Since only unregister_kprobe() calls arch_remove_kprobe(), and only
    after having removed the struct kprobe from the kprobes list (while the
    kprobes mutex is held), I wonder if there is any need to hold the
    kprobes mutex at all when calling arch_remove_kprobe(). It turns out
    that only get_insn_slot()/free_insn_slot() (which is in
    kernel/kprobes.c, but called from arch specific code) seems to really
    use protection of this mutex.

    Would it make sense to protect the kprobe_insn_pages list with a
    new kprobe_insn_mutex, nestable in the kprobe_mutex ?

    Mathieu Desnoyers
    Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal
    OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68
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