Re: [PATCH 3/3] ftrace: add ability to only trace swapper tasks

From: Ingo Molnar
Date: Thu Dec 04 2008 - 03:07:06 EST

* Steven Rostedt <rostedt@xxxxxxxxxxx> wrote:

> From: Steven Rostedt <srostedt@xxxxxxxxxx>
> Impact: New feature
> This patch lets the swapper tasks of all CPUS be filtered by the
> set_ftrace_pid file.
> If '0' is echoed into this file, then all the idle tasks (aka swapper)
> is flagged to be traced. This affects all CPU idle tasks.
> Signed-off-by: Steven Rostedt <srostedt@xxxxxxxxxx>
> ---
> kernel/trace/ftrace.c | 74 +++++++++++++++++++++++++++++++++++++++++-------
> 1 files changed, 63 insertions(+), 11 deletions(-)

okay, i've applied it - but i dont like the extra complexity of +50 lines
at all.

This is an area where the 'PID namespaces via struct pid pointers' model
breaks down and forces collateral complexity into other subsystems, and
where a simple integer based filter is so intuitive.

Eric, can you see any way to simplify this? It looks horrible.

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