Currently, If the 'rcu_nocb_poll' bootargs is enable, all rcuog kthreads
enter polling mode. however, due to only insert CPU's rdp which belong to
rcu_nocb_mask to 'nocb_head_rdp' list or all CPU's rdp served by rcuog
kthread have been de-offloaded, these cause the 'nocb_head_rdp' list
served by rcuog kthread is empty, when the 'nocb_head_rdp' is empty,
the rcuog kthread in polling mode not actually do anything. fix it by
exiting polling mode when the 'nocb_head_rdp'list is empty, otherwise
entering polling mode.
Signed-off-by: Zqiang <qiang1.zhang@xxxxxxxxx>
---
v1->v2:
Move rcu_nocb_poll flags check from rdp_offload_toggle() to
rcu_nocb_rdp_offload/deoffload(), avoid unnecessary setting of
rdp_gp->nocb_gp_sleep flags, because when rcu_nocb_poll is set
the rdp_gp->nocb_gp_sleep is not used.
kernel/rcu/tree_nocb.h | 16 ++++++++++------
1 file changed, 10 insertions(+), 6 deletions(-)
diff --git a/kernel/rcu/tree_nocb.h b/kernel/rcu/tree_nocb.h
index fa8e4f82e60c..2a52c9abc681 100644
--- a/kernel/rcu/tree_nocb.h
+++ b/kernel/rcu/tree_nocb.h
@@ -698,10 +698,14 @@ static void nocb_gp_wait(struct rcu_data *my_rdp)
TPS("WakeBypassIsDeferred"));
}
if (rcu_nocb_poll) {
- /* Polling, so trace if first poll in the series. */
- if (gotcbs)
- trace_rcu_nocb_wake(rcu_state.name, cpu, TPS("Poll"));
- schedule_timeout_idle(1);
+ if (list_empty(&my_rdp->nocb_head_rdp)) {
+ rcu_wait(READ_ONCE(my_rdp->nocb_toggling_rdp));
+ } else {
+ /* Polling, so trace if first poll in the series. */
+ if (gotcbs)
+ trace_rcu_nocb_wake(rcu_state.name, cpu, TPS("Poll"));
+ schedule_timeout_idle(1);
+ }
} else if (!needwait_gp) {
/* Wait for callbacks to appear. */
trace_rcu_nocb_wake(rcu_state.name, cpu, TPS("Sleep"));
@@ -1030,7 +1034,7 @@ static long rcu_nocb_rdp_deoffload(void *arg)
mutex_lock(&rdp_gp->nocb_gp_kthread_mutex);
if (rdp_gp->nocb_gp_kthread) {
- if (wake_gp)
+ if (wake_gp || rcu_nocb_poll)
wake_up_process(rdp_gp->nocb_gp_kthread);
/*
@@ -1152,7 +1156,7 @@ static long rcu_nocb_rdp_offload(void *arg)
* rcu_nocb_unlock() rcu_nocb_unlock()
*/
wake_gp = rdp_offload_toggle(rdp, true, flags);
- if (wake_gp)
+ if (wake_gp || rcu_nocb_poll)
wake_up_process(rdp_gp->nocb_gp_kthread);
swait_event_exclusive(rdp->nocb_state_wq,
rcu_segcblist_test_flags(cblist, SEGCBLIST_KTHREAD_CB) &&
--
2.25.1
