[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <y0mskv6y3va.fsf@ton.toronto.redhat.com>
Date: Sat, 21 Jun 2008 15:39:21 -0400
From: fche@...hat.com (Frank Ch. Eigler)
To: Steven Rostedt <rostedt@...dmis.org>
Cc: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
Masami Hiramatsu <mhiramat@...hat.com>,
Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>,
Peter Zijlstra <peterz@...radead.org>,
Ingo Molnar <mingo@...e.hu>,
LKML <linux-kernel@...r.kernel.org>,
systemtap-ml <systemtap@...rces.redhat.com>,
Hideo AOKI <haoki@...hat.com>
Subject: Re: [RFC][Patch 2/2] markers: example of irq regular kernel markers
Steven Rostedt <rostedt@...dmis.org> writes:
> [...]
>> That is not so. They are far from panaceanic, but printf formats are
>> useful for type checked simple scalars, which we can extract and use
>> for purposes other than printf like operations.
>
> It doesn't help much if you mix a pid and prio of a task_struct, and then
> use the prio to find the actual task, or try setting another task priority
> to the pid.
Right, though the same is true for a tracer client flipping around
"next" and "prev" pointer values.
>[...]
>> > Passing in a pointer to the structure being traced should be enough
>> > for all tracers.
>>
>> On the contrary, we have explained why *this is not so*. Using raw
>> general structure pointers in impractical for some tracers.
>
> The thing that those tracers need is something that can be stored in the
> kernel that can easily extract the needed information.
Well sure, but who is to do that storage & extraction? Some code the
marker site maintainer needs to write for each marker?
> [...]
>> Maybe a solution could involve some restrictions on the generalities.
>> For example, can we narrow down the number of different scalar +
>> pointer types to a fixed handful? Can we tolerate type-safety being
>> provided by families of function declarations rather than one generic
>> one?
>
> I'm all for restricting this, I even suggested something similar a while
> ago (http://lists.openwall.net/linux-kernel/2006/10/07/21). No, I'm not
> pushing that solution, that solution was only to bring out more ideas.
Parts of that approach have a lot of merit. Perhaps we should spend
some time cataloguing the types of all the lttng/logdev/blktrace
"markers" and their nearby pointers. Maybe it's only a few dozen
types altogether.
- FChE
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists