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

Jiri Olsa
2016-03-11T18:15:21Z

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

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

thanks,
jirka