On Wed, Nov 18, 2020 at 11:15:41AM -0500, Joel Fernandes (Google) wrote:
> After rcu_do_batch(), add a check for whether the seglen counts went to
> zero if the list was indeed empty.
>
> Signed-off-by: Joel Fernandes (Google) <joel@xxxxxxxxxxxxxxxxx>
Queued for testing and further review, thank you!
Thanx, Paul
> ---
> v1->v2: Added more debug checks.
>
> kernel/rcu/rcu_segcblist.c | 12 ++++++++++++
> kernel/rcu/rcu_segcblist.h | 3 +++
> kernel/rcu/tree.c | 2 ++
> 3 files changed, 17 insertions(+)
>
> diff --git a/kernel/rcu/rcu_segcblist.c b/kernel/rcu/rcu_segcblist.c
> index 5059b6102afe..6e98bb3804f0 100644
> --- a/kernel/rcu/rcu_segcblist.c
> +++ b/kernel/rcu/rcu_segcblist.c
> @@ -94,6 +94,18 @@ static long rcu_segcblist_get_seglen(struct rcu_segcblist *rsclp, int seg)
> return READ_ONCE(rsclp->seglen[seg]);
> }
>
> +/* Return number of callbacks in segmented callback list by totalling seglen. */
> +long rcu_segcblist_n_segment_cbs(struct rcu_segcblist *rsclp)
> +{
> + long len = 0;
> + int i;
> +
> + for (i = RCU_DONE_TAIL; i < RCU_CBLIST_NSEGS; i++)
> + len += rcu_segcblist_get_seglen(rsclp, i);
> +
> + return len;
> +}
> +
> /* Set the length of a segment of the rcu_segcblist structure. */
> static void rcu_segcblist_set_seglen(struct rcu_segcblist *rsclp, int seg, long v)
> {
> diff --git a/kernel/rcu/rcu_segcblist.h b/kernel/rcu/rcu_segcblist.h
> index cd35c9faaf51..46a42d77f7e1 100644
> --- a/kernel/rcu/rcu_segcblist.h
> +++ b/kernel/rcu/rcu_segcblist.h
> @@ -15,6 +15,9 @@ static inline long rcu_cblist_n_cbs(struct rcu_cblist *rclp)
> return READ_ONCE(rclp->len);
> }
>
> +/* Return number of callbacks in segmented callback list by totalling seglen. */
> +long rcu_segcblist_n_segment_cbs(struct rcu_segcblist *rsclp);
> +
> void rcu_cblist_init(struct rcu_cblist *rclp);
> void rcu_cblist_enqueue(struct rcu_cblist *rclp, struct rcu_head *rhp);
> void rcu_cblist_flush_enqueue(struct rcu_cblist *drclp,
> diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> index f5b61e10f1de..91e35b521e51 100644
> --- a/kernel/rcu/tree.c
> +++ b/kernel/rcu/tree.c
> @@ -2553,6 +2553,8 @@ static void rcu_do_batch(struct rcu_data *rdp)
> WARN_ON_ONCE(count == 0 && !rcu_segcblist_empty(&rdp->cblist));
> WARN_ON_ONCE(!IS_ENABLED(CONFIG_RCU_NOCB_CPU) &&
> count != 0 && rcu_segcblist_empty(&rdp->cblist));
> + WARN_ON_ONCE(count == 0 && rcu_segcblist_n_segment_cbs(&rdp->cblist) != 0);
> + WARN_ON_ONCE(count != 0 && rcu_segcblist_n_segment_cbs(&rdp->cblist) == 0);
>
> rcu_nocb_unlock_irqrestore(rdp, flags);
>
> --
> 2.29.2.299.gdc1121823c-goog
