The __call_rcu_nocb_wake() function and its predecessors set
->qlen_last_fqs_check to zero for the first callback and to LONG_MAX / 2
for forced reawakenings. The former can result in a too-quick reawakening
when there are many callbacks ready to invoke and the latter prevents a
second reawakening. This commit therefore sets ->qlen_last_fqs_check
to the current number of callbacks in both cases. While in the area,
this commit also moves both assignments under ->nocb_lock.
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxx>
---
kernel/rcu/tree_plugin.h | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index c1dfbac8cd39..297b38732e28 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -1626,6 +1626,7 @@ static void __call_rcu_nocb_wake(struct rcu_data *rdp, bool was_alldone,
// Need to actually to a wakeup.
len = rcu_segcblist_n_cbs(&rdp->cblist);
if (was_alldone) {
+ rdp->qlen_last_fqs_check = len;
if (!irqs_disabled_flags(flags)) {
/* ... if queue was empty ... */
wake_nocb_gp(rdp, false, flags);
@@ -1636,9 +1637,9 @@ static void __call_rcu_nocb_wake(struct rcu_data *rdp, bool was_alldone,
TPS("WakeEmptyIsDeferred"));
rcu_nocb_unlock_irqrestore(rdp, flags);
}
- rdp->qlen_last_fqs_check = 0;
} else if (len > rdp->qlen_last_fqs_check + qhimark) {
/* ... or if many callbacks queued. */
+ rdp->qlen_last_fqs_check = len;
if (!irqs_disabled_flags(flags)) {
wake_nocb_gp(rdp, true, flags);
trace_rcu_nocb_wake(rcu_state.name, rdp->cpu,
@@ -1648,7 +1649,6 @@ static void __call_rcu_nocb_wake(struct rcu_data *rdp, bool was_alldone,
TPS("WakeOvfIsDeferred"));
rcu_nocb_unlock_irqrestore(rdp, flags);
}
- rdp->qlen_last_fqs_check = LONG_MAX / 2;
} else {
trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, TPS("WakeNot"));
rcu_nocb_unlock_irqrestore(rdp, flags);
--
2.17.1
