Re: [PATCH] context_tracking: Add comments on interface andinternals

[Andrew Morton]

On Thu, 13 Dec 2012 23:50:23 +0100
Frederic Weisbecker <fweisbec@xxxxxxxxx> wrote:

> >
> >> + * This call supports re-entrancy.
> >
> > Presumably the explanation for user_exit() applies here.
> 
> Not sure what you mean here.

It's unclear what it means to say "user_enter() supports reentrancy". 
I mean, zillions of kernel functions are surely reentrant - so what? 
It appears that you had something in mind when pointing this out, but
what was it?  The comment over user_exit() appears to tell us.

> > It's mainly this bit which makes me wonder why the code is in lib/.  Is
> > there any conceivable prospect that any other subsystem will use this
> > code for anything?
> 
> So that's because of that cputime accounting on dynticks CPUs which
> will need to know about user/kernel transitions. I'm preparing that
> for the 3.9 merge window.

Oh.  That's really the entire reason for the patch and should have been
in the changelog!
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