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    SubjectRe: [PATCH 0/8] [GIT PULL] TRACE_EVENT for modules
    * Ingo Molnar (mingo@elte.hu) wrote:
    >
    > * Jeremy Fitzhardinge <jeremy@goop.org> wrote:
    >
    > > Steven Rostedt wrote:
    > >> On Tue, 14 Apr 2009, Jeremy Fitzhardinge wrote:
    > >>
    > >>
    > >>> Theodore Tso wrote:
    > >>>
    > >>>> Any chance you could support something like this?
    > >>>>
    > >>>>
    > >>> I think that's already there. I'm defining
    > >>> arch/x86/include/asm/paravirt-trace.h with:
    > >>>
    > >>> #ifndef _ASM_X86_PARAVIRT_TRACE_H
    > >>> #define _ASM_X86_PARAVIRT_TRACE_H
    > >>>
    > >>> #include <linux/tracepoint.h>
    > >>> #include <asm/paravirt_types.h>
    > >>>
    > >>> #undef TRACE_SYSTEM
    > >>> #define TRACE_SYSTEM pvops
    > >>>
    > >>> #define TRACE_INCLUDE_FILE paravirt-trace
    > >>> #define TRACE_INCLUDE_PATH asm
    > >>> [...]
    > >>>
    > >>>
    > >>> Which ends up including <asm/paravirt-trace.h>
    > >>>
    > >>
    > >> Not quite. It ends up looking like
    > >>
    > >> #include "asm/paravirt-trace.h"
    > >>
    > >> As long as there is no "asm" directory in the include/trace directory,
    > >> I think that is fine.
    > >
    > > OK.
    > >
    > > I'm having a bit of trouble with paravirt-trace.h when I actually
    > > include it in paravirt.h. asm/paravirt.h is itself included in
    > > lots of places, and so its fairly easy to end up with cyclic
    > > include dependencies which are fairly painful. In this case I'm
    > > seeing asm/paravirt.h -> linux/tracepoint.h -> linux/rcupate.h ->
    > > {lots of stuff}, which gives errors like:
    >
    > tracepoint.h should not include any complex headers like rcupdate.h.
    >
    > > I'm wondering if there's much downside in making the code
    > > __DO_TRACE() out of line so that we can make tracepoint.h have
    > > absolutely minimal include dependencies?
    >
    > yeah.
    >
    > And besides, the rcu_read_lock_sched_notrace() there should probably
    > be a preempt_disable_notrace() / preempt_enable_notrace() variant.
    > (it's sligtly faster that way and we better be atomic and
    > self-sufficient in tracepoints anyway)
    >

    Yes, rcu_read_(un)lock_sched_notrace maps directly to
    preempt_(en/dis)able_notrace. But for RCU verifiability's sake, I made
    sure to create rcu_read_lock versions of these primitives instead of
    simply using preempt_disable. Maybe we should simply take those
    low-level primitives out of rcupdate.h and put them in a simpler header?

    Mathieu


    > Ingo
    >

    --
    Mathieu Desnoyers
    OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68


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