RE: [PATCH 3/8] scsi: ufshpb: Add region's reads counter

[Avri Altman]

> >
> > +     if (ufshpb_mode == HPB_HOST_CONTROL)
> > +             reads = atomic64_inc_return(&rgn->reads);
> > +
> >       if (!ufshpb_is_support_chunk(transfer_len))
> >               return;
> >
> > +     if (ufshpb_mode == HPB_HOST_CONTROL) {
> > +             /*
> > +              * in host control mode, reads are the main source for
> > +              * activation trials.
> > +              */
> > +             if (reads == ACTIVATION_THRSHLD) {
Oops - this is a bug...

> > +
> > +     /* region reads - for host mode */
> > +     atomic64_t reads;
> 
> Why do you need an atomic variable for this?  What are you trying to
> "protect" here by flushing the cpus all the time?  What protects this
> variable from changing right after you have read from it (hint, you do
> that above...)
> 
> atomics are not race-free, use a real lock if you need that.
We are on the data path here - this is called from queuecommand.
The "reads" counter is being symmetrically read and written,
so adding a spin lock here might become a source for contention.

Also I am not worried about the exact value of this counter, except of one place - 
See above.  Will fix it.

Thanks,
Avri