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

[Eric W. Biederman]

Steven Rostedt <rostedt at goodmis.org> writes:

> On Thu, 4 Dec 2008, Eric W. Biederman wrote:
>
>> Ingo Molnar <mingo at elte.hu> writes:
>> 
>> > * Andrew Morton <akpm at linux-foundation.org> wrote:
>> >
>> >> > Signed-off-by: Steven Rostedt <srostedt at redhat.com>
>> >> 
>> >> What does this patch actually do?  Is swapper currently excluded from 
>> >> tracing for undisclosed reasons and this patch permits it to be traced? 
>> >> If so, why was swapper thus excluded?  Or am I totally off track?
>> >
>> >> > +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.

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.

Eric

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