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

[Steven Rostedt]

On Thu, 4 Dec 2008, Eric W. Biederman wrote:
> >> >
> >> >> > +static struct pid * const ftrace_swapper_pid = (struct pid *)1;
> >> >> 
> >> >> eh?
> >> >
> >> > all side-effects of getting rid of the integer based PID namespace and 
> >> > replacing them with struct pid pointers.
> >> 
> >> Thanks for asking Andrew it looks like an unnecessary side effect.
> >
> > Well, it was necessary without hacking fork.c ;-)
> 
> The (struct pid *)1 has always been unnecessary.

Well, I could set it to the &init_struct_pid as you said, but it will not 
change any of the code below it. So it does not matter what 
ftrace_swapper_pid is set to, as long as it is not set to something that 
can be a legitimate pid struct for something not the swapper task.

It will only matter when we fix the fork code.

> 
> As for fork.  It would be nice to remove most of the special cases
> for the idle thread.  At least the counts are significant.  The rest
> is pretty much a don't care at this point.

Well, the swapper task should still have a pid of zero. That is probably 
important.

-- Steve