Re: [PATCH 4/5] ftrace: Make ftrace_hash_rec_enable return update bool

Namhyung Kim
2016-03-12T08:36:37Z

Hi Jiri,

On Fri, Mar 11, 2016 at 07:15:06PM +0100, Jiri Olsa wrote:
> On Fri, Mar 11, 2016 at 11:28:00PM +0900, Namhyung Kim wrote:
>
> SNIP
>
> > > @@ -1694,7 +1695,7 @@ static void __ftrace_hash_rec_update(struct ftrace_ops *ops,
> > > if (inc) {
> > > rec->flags++;
> > > if (FTRACE_WARN_ON(ftrace_rec_count(rec) == FTRACE_REF_MAX))
> > > - return;
> > > + return false;
> > >
> > > /*
> > > * If there's only a single callback registered to a
> > > @@ -1720,7 +1721,7 @@ static void __ftrace_hash_rec_update(struct ftrace_ops *ops,
> > > rec->flags |= FTRACE_FL_REGS;
> > > } else {
> > > if (FTRACE_WARN_ON(ftrace_rec_count(rec) == 0))
> > > - return;
> > > + return false;
> > > rec->flags--;
> > >
> > > /*
> > > @@ -1753,22 +1754,27 @@ static void __ftrace_hash_rec_update(struct ftrace_ops *ops,
> > > */
> > > }
> > > count++;
> > > +
> > > + update |= ftrace_test_record(rec, 1) != FTRACE_UPDATE_IGNORE;
> >
> > Shouldn't it use 'inc' instead of 1 for the second argument of
> > the ftrace_test_record()?
>
> I dont think so, 1 is to update calls (FTRACE_UPDATE_CALLS)
> check ftrace_modify_all_code:
>
> if (command & FTRACE_UPDATE_CALLS)
> ftrace_replace_code(1);
> else if (command & FTRACE_DISABLE_CALLS)
> ftrace_replace_code(0);
>
> both ftrace_startup, ftrace_shutdown use FTRACE_UPDATE_CALLS

Ah, ok. So the second argument of the ftrace_test_record() is not
'enable' actually.. :-/

>
> you'd use 0 only to disable all, check ftrace_check_record comments:
>
> /*
> * If we are updating calls:
> *
> * If the record has a ref count, then we need to enable it
> * because someone is using it.
> *
> * Otherwise we make sure its disabled.
> *
> * If we are disabling calls, then disable all records that
> * are enabled.
> */
> if (enable && ftrace_rec_count(rec))
> flag = FTRACE_FL_ENABLED;
>
>
> used by ftrace_shutdown_sysctl

I got it. Thank you for the explanation!

Thanks,
Namhyung