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authorPaul E. McKenney <paulmck@linux.ibm.com>2019-05-23 10:43:58 -0700
committerPaul E. McKenney <paulmck@linux.ibm.com>2019-08-13 14:35:49 -0700
commitaeeacd9d844b2219d47e9010298b635c68a2a4c9 (patch)
tree25d875d28d600c3aebd746fbe0174c207f824238 /kernel/rcu
parent0bd55c693617cd2488378d011b66b92e1dd66ecf (diff)
rcu/nocb: Enable re-awakening under high callback load
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@linux.ibm.com>
Diffstat (limited to 'kernel/rcu')
-rw-r--r--kernel/rcu/tree_plugin.h4
1 files changed, 2 insertions, 2 deletions
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index ae927710d670..7077ef7bea96 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -1628,6 +1628,7 @@ 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);
@@ -1638,9 +1639,9 @@ 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,
@@ -1650,7 +1651,6 @@ 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);