On Tue, Jul 11, 2017 at 02:17:47PM -0700, Shivappa Vikas wrote:
>
>
> On Thu, 6 Jul 2017, Thomas Gleixner wrote:
>
> > On Thu, 6 Jul 2017, Shivappa Vikas wrote:
> > > On Sun, 2 Jul 2017, Thomas Gleixner wrote:
> > > > > +static bool __mon_event_count(u32 rmid, struct rmid_read *rr)
> > > > > +{
> > > > > + u64 tval;
> > > > > +
> > > > > + tval = __rmid_read(rmid, rr->evtid);
> > > > > + if (tval & (RMID_VAL_ERROR | RMID_VAL_UNAVAIL)) {
> > > > > + rr->val = tval;
> > > > > + return false;
> > > > > + }
> > > > > + switch (rr->evtid) {
> > > > > + case QOS_L3_OCCUP_EVENT_ID:
> > > > > + rr->val += tval;
> > > > > + return true;
> > > > > + default:
> > > > > + return false;
> > > >
> > > > I have no idea what that return code means.
> > >
> > > false for the invalid event id and all errors for __rmid_read. (IOW all
> > > errors
> > > for __mon_event-read)
> >
> > Sure, but why bool? What's wrong with proper error return codes, so issues
> > can be distinguished and potentially propagated in the callchain?
>
> Ok, The error is propagated wih the rr->val actually. is this better?
>
> Hardware throws the RMID_VAL_ERROR (bit 63) when an invalid RMID or
> event is written to event select - this case seems similar.
>
> default:
> rr->val = RMID_VAL_ERROR;
> return -EINVAL;
> }
I'll take the blame for not documenting this better. What's going
on here is that we are calculating the sum of some list of RMIDs
(for the case where we read a mon_data/*/* file for a CTRL_MON group
that has some MON subgroups ... when reading a from a MON group there
is only one RMID).
Now we might get an error reading one of those (either or both of
RMID_VAL_ERROR and RMID_VAL_UNAVAIL bits set). In which case we can't
compute the sum, and there is no point in reading any more RMIDs.
So the return of this function is:
true: I read this RMID OK and added it to rr->val
false: I got an error. Give up. The error type is in the high bits of rr->val
-Tony
