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

From: Eric W. Biederman
Date: Fri Dec 05 2008 - 02:46:41 EST

Steven Rostedt <rostedt@xxxxxxxxxxx> writes:

> On Thu, 4 Dec 2008, Eric W. Biederman wrote:
>> Right. I simply meant most of the
>> if (likely(p->pid)) conditional except for the counts is pretty much a don't
>> care. Keeping the idle tasks off of the process list and out of the counts
>> is useful.
>> For this particular case what problem did you see with calling attach_pid
>> with PIDTYPE_PID on init_struct_pid?
> On boot up, the CPU 0 idle task is attached to init_struct_pid, and not
> the others. If you do a "attach_pid" on the next idle task that is created,
> it will become the attched process, bumping off CPU 0's idle task from the
> init_struct_pid.

It should form a linked list. For other pid types we don't have a problem.

> When doing the code you suggested, I end up with only marking the last
> idle task to be created.

Odd. It is all a linked list through the task structures.
I'm guessing the initialization isn't quite right.



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