On Fri, Nov 06, 2020 at 07:01:57PM -0500, Joel Fernandes wrote:
> On Wed, Nov 04, 2020 at 09:01:33AM -0800, Paul E. McKenney wrote:
>
> > A casual reader might be forgiven for being confused by the combination
> > of "Return" in the above comment and the "void" function type below.
> > So shouldn't this comment be something like "Add the specified number
> > of callbacks to the specified segment..."?
>
> You are right, sorry and will fix it.
>
> > > @@ -330,11 +342,16 @@ void rcu_segcblist_extract_pend_cbs(struct
> > > rcu_segcblist *rsclp,
> > >
> > > if (!rcu_segcblist_pend_cbs(rsclp))
> > > return; /* Nothing to do. */
> > > + rclp->len = rcu_segcblist_get_seglen(rsclp, RCU_WAIT_TAIL) +
> > > + rcu_segcblist_get_seglen(rsclp, RCU_NEXT_READY_TAIL) +
> > > + rcu_segcblist_get_seglen(rsclp, RCU_NEXT_TAIL);
> >
> > This should be a "for" loop. Yes, the number and names of the segments
> > hasn't changed for a good long time, but nothing like code as above to
> > inspire Murphy to more mischief. :-/
> >
> > Actually, why not put the summation in the existing "for" loop below?
> > That would save a line of code in addition to providing less inspiration
> > for Mr. Murphy.
>
> I can do that. Actually Frederic suggested the same thing but I was reluctant
> as I felt it did not give much LOC benefit. Will revisit it.
It reduces 1 line of code :) I changed it to the below, will update the patch:
---8<-----------------------
diff --git a/kernel/rcu/rcu_segcblist.c b/kernel/rcu/rcu_segcblist.c
index 9b43d686b1f3..bff9b2253e50 100644
--- a/kernel/rcu/rcu_segcblist.c
+++ b/kernel/rcu/rcu_segcblist.c
@@ -101,7 +101,7 @@ static void rcu_segcblist_set_seglen(struct rcu_segcblist
*rsclp, int seg, long
WRITE_ONCE(rsclp->seglen[seg], v);
}
-/* Return number of callbacks in a segment of the segmented callback list. */
+/* Increase the numeric length of a segment by a specified amount. */
static void rcu_segcblist_add_seglen(struct rcu_segcblist *rsclp, int seg,
long v)
{
WRITE_ONCE(rsclp->seglen[seg], rsclp->seglen[seg] + v);
@@ -406,13 +406,12 @@ void rcu_segcblist_extract_pend_cbs(struct rcu_segcblist
*rsclp,
if (!rcu_segcblist_pend_cbs(rsclp))
return; /* Nothing to do. */
- rclp->len = rcu_segcblist_get_seglen(rsclp, RCU_WAIT_TAIL) +
- rcu_segcblist_get_seglen(rsclp, RCU_NEXT_READY_TAIL) +
- rcu_segcblist_get_seglen(rsclp, RCU_NEXT_TAIL);
+ rclp->len = 0;
*rclp->tail = *rsclp->tails[RCU_DONE_TAIL];
rclp->tail = rsclp->tails[RCU_NEXT_TAIL];
WRITE_ONCE(*rsclp->tails[RCU_DONE_TAIL], NULL);
for (i = RCU_DONE_TAIL + 1; i < RCU_CBLIST_NSEGS; i++) {
+ rclp->len += rcu_segcblist_get_seglen(rsclp, i);
WRITE_ONCE(rsclp->tails[i], rsclp->tails[RCU_DONE_TAIL]);
rcu_segcblist_set_seglen(rsclp, i, 0);
}
