On Sun, Oct 11, 2020 at 09:35:37AM -0700, Joel Fernandes wrote:
> On Fri, Oct 9, 2020 at 4:14 PM Frederic Weisbecker <[email protected]>
> wrote:
> >
> > On Wed, Sep 23, 2020 at 11:22:08AM -0400, Joel Fernandes (Google) wrote:
> > > Currently, rcu_do_batch() depends on the unsegmented callback list's len
> > > field
> > > to know how many CBs are executed. This fields counts down from 0 as CBs
> > > are
> > > dequeued. It is possible that all CBs could not be run because of
> > > reaching
> > > limits in which case the remaining unexecuted callbacks are requeued in
> > > the
> > > CPU's segcblist.
> > >
> > > The number of callbacks that were not requeued are then the negative
> > > count (how
> > > many CBs were run) stored in the rcl->len which has been counting down on
> > > every
> > > dequeue. This negative count is then added to the per-cpu segmented
> > > callback
> > > list's to correct its count.
> > >
> > > Such a design works against future efforts to track the length of each
> > > segment
> > > of the segmented callback list. The reason is because
> > > rcu_segcblist_extract_done_cbs() will be populating the unsegmented
> > > callback
> > > list's length field (rcl->len) during extraction.
> > > Also, the design of counting down from 0 is confusing and error-prone
> > > IMHO.
> >
> > Right :)
>
> :)
>
> > > This commit therefore explicitly counts have many callbacks were executed
> > > in
> >
> > s/have/how
> >
> > > rcu_do_batch() itself, and uses that to update the per-CPU segcb list's
> > > ->len
> > > field, without relying on the negativity of rcl->len.
> > >
> > > Signed-off-by: Joel Fernandes (Google) <[email protected]>
> >
> > Reviewed-by: Frederic Weisbecker <[email protected]>
>
> Thanks! Paul would be Ok to make the minor fixup s/have/how/ that
> Frederic pointed?
But of course! I was waiting until Frederic gets them all reviewed,
with an eye to applying and wordsmithing them as a set.
> - Joel
> (Due to COVID issues at home, I'm intermittently working so advance
> apologies for slow replies.)
And I hope that this is going as well as it possibly can!
Thanx, Paul
