linux-kernel - Re: [PATCH 2/2] perf lock: Fix output of tracing lock events

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Date:	Sat, 26 Dec 2009 22:43:44 +0900
From:	Hitoshi Mitake <mitake@....info.waseda.ac.jp>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	mingo@...e.hu, linux-kernel@...r.kernel.org,
	Paul Mackerras <paulus@...ba.org>,
	Frederic Weisbecker <fweisbec@...il.com>
Subject: Re: [PATCH 2/2] perf lock: Fix output of tracing lock events

Sorry for my slow response...

>> diff --git a/include/trace/events/lock.h b/include/trace/events/lock.h
>> index a870ba1..2f94e25 100644
>> --- a/include/trace/events/lock.h
>> +++ b/include/trace/events/lock.h
>> @@ -18,16 +18,19 @@ TRACE_EVENT(lock_acquire,
>>       TP_ARGS(lock, subclass, trylock, read, check, next_lock, ip),
>>
>>       TP_STRUCT__entry(
>> +             __field(struct lockdep_map *, lockdep_addr)
>>               __field(unsigned int, flags)
>>               __string(name, lock->name)
>>       ),
>
> I feel a bit awkward explicitly leaking kernel pointers like that. All
> this is accessible by root only (for now) so its not too harmfull, but
> sitll.
>
> Also, I don't think we want to expose the struct lockdep_map thing, a
> regular void * would be better.

Yeah, I agree with it. void * is enough.

>
> As to removing the waittime, I'm not sure, in this case, yes, but if you
> want some other processing that hooks straight into the tracepoints
> instead of using a logging structure, it might be useful.
>
> Removing that do_div() from there and exposing waittime as u64 in nsec,
> for sure, that do_div() is just silly.
>
>
>

I was too egoist. perf lock is not an only one user of lock events.

And I have a suggestion. Adding name of source files and lines of
lock instances may be good thing for human's readability.
How do you think?

I have some pending works for these (not made into patches).
If you agree, I'll send these later.
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