[PATCH rcu 05/16] rcu: Refactor code a bit in rcu_nocb_do_flush_bypass()

From: Paul E. McKenney
Date: Wed Nov 30 2022 - 13:14:29 EST


From: "Joel Fernandes (Google)" <joel@xxxxxxxxxxxxxxxxx>

This consolidates the code a bit and makes it cleaner. Functionally it
is the same.

Reported-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
Signed-off-by: Joel Fernandes (Google) <joel@xxxxxxxxxxxxxxxxx>
Reviewed-by: Frederic Weisbecker <frederic@xxxxxxxxxx>
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
---
kernel/rcu/tree_nocb.h | 17 +++++++++--------
1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/kernel/rcu/tree_nocb.h b/kernel/rcu/tree_nocb.h
index d6e4c076b0515..213daf81c057f 100644
--- a/kernel/rcu/tree_nocb.h
+++ b/kernel/rcu/tree_nocb.h
@@ -327,10 +327,11 @@ static void wake_nocb_gp_defer(struct rcu_data *rdp, int waketype,
*
* Note that this function always returns true if rhp is NULL.
*/
-static bool rcu_nocb_do_flush_bypass(struct rcu_data *rdp, struct rcu_head *rhp,
+static bool rcu_nocb_do_flush_bypass(struct rcu_data *rdp, struct rcu_head *rhp_in,
unsigned long j, bool lazy)
{
struct rcu_cblist rcl;
+ struct rcu_head *rhp = rhp_in;

WARN_ON_ONCE(!rcu_rdp_is_offloaded(rdp));
rcu_lockdep_assert_cblist_protected(rdp);
@@ -345,16 +346,16 @@ static bool rcu_nocb_do_flush_bypass(struct rcu_data *rdp, struct rcu_head *rhp,

/*
* If the new CB requested was a lazy one, queue it onto the main
- * ->cblist so we can take advantage of a sooner grade period.
+ * ->cblist so that we can take advantage of the grace-period that will
+ * happen regardless. But queue it onto the bypass list first so that
+ * the lazy CB is ordered with the existing CBs in the bypass list.
*/
if (lazy && rhp) {
- rcu_cblist_flush_enqueue(&rcl, &rdp->nocb_bypass, NULL);
- rcu_cblist_enqueue(&rcl, rhp);
- WRITE_ONCE(rdp->lazy_len, 0);
- } else {
- rcu_cblist_flush_enqueue(&rcl, &rdp->nocb_bypass, rhp);
- WRITE_ONCE(rdp->lazy_len, 0);
+ rcu_cblist_enqueue(&rdp->nocb_bypass, rhp);
+ rhp = NULL;
}
+ rcu_cblist_flush_enqueue(&rcl, &rdp->nocb_bypass, rhp);
+ WRITE_ONCE(rdp->lazy_len, 0);

rcu_segcblist_insert_pend_cbs(&rdp->cblist, &rcl);
WRITE_ONCE(rdp->nocb_bypass_first, j);
--
2.31.1.189.g2e36527f23