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Subject[PATCH] rcu/segcblist: Add debug check for whether seglen is 0 for empty list
Date
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@joelfernandes.org>

---
kernel/rcu/rcu_segcblist.c | 12 ++++++++++++
kernel/rcu/rcu_segcblist.h | 3 +++
kernel/rcu/tree.c | 1 +
3 files changed, 16 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..928bd10c9c3b 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -2553,6 +2553,7 @@ 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));

rcu_nocb_unlock_irqrestore(rdp, flags);

--
2.29.2.299.gdc1121823c-goog
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