On Mon, Apr 14, 2025 at 08:07:54AM +0200, Christoph Hellwig wrote:
> On Mon, Apr 14, 2025 at 08:54:36AM +0800, Ming Lei wrote:
> > > > elv_iosched_load_module(name);
> > > >
> > > > + idx = srcu_read_lock(&set->update_nr_hwq_srcu);
> > > > +
> > > > + if (set->flags & BLK_MQ_F_UPDATE_HW_QUEUES) {
> > >
> > > What provides atomicity for field modifications vs reading of set->flags?
> > > i.e. does this need to switch using test/set_bit?
> >
> > WRITE is serialized via tag set lock with synchronize_srcu().
> >
> > READ is covered by srcu read lock.
> >
> > It is typical RCU usage, one writer vs. multiple writer.
>
> No, (S)RCU does not help you with atomicy of bitfields.
OK, will change it into one state variable.
Thanks,
Ming
