Re: [PATCH 0/8] [GIT PULL] TRACE_EVENT for modules

Ingo Molnar
2009-04-15T08:31:12Z

* 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)

Ingo