When CONFIG_PREEMPT_RT=y, the rcutree.kthread_prio command-line
parameter signals initialization code to boost the priority of rcuc
callbacks to the designated value. With the additional
CONFIG_RCU_NOCB_CPU=y configuration and an additional rcu_nocbs
command-line parameter, the callbacks on the listed cores are
offloaded to new rcuop threads that are not pinned to the cores whose
post-grace-period work is performed. While the rcuop threads perform
the same function as the rcuc threads they offload, the kthread_prio
parameter only boosts the priority of the rcuc threads. Fix this
inconsistency by elevating rcuop threads to the same priority as rcuc
ones.
Signed-off-by: Alison Chaiken <[email protected]>
---
kernel/rcu/tree.c | 2 +-
kernel/rcu/tree_nocb.h | 3 +++
2 files changed, 4 insertions(+), 1 deletion(-)
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 15cabb288a1c..ba9eaa9a72b0 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -153,7 +153,7 @@ static void sync_sched_exp_online_cleanup(int cpu);
static void check_cb_ovld_locked(struct rcu_data *rdp, struct rcu_node *rnp);
static bool rcu_rdp_is_offloaded(struct rcu_data *rdp);
-/* rcuc/rcub kthread realtime priority */
+/* rcuc/rcub/rcuop kthread realtime priority */
static int kthread_prio = IS_ENABLED(CONFIG_RCU_BOOST) ? 1 : 0;
module_param(kthread_prio, int, 0444);
diff --git a/kernel/rcu/tree_nocb.h b/kernel/rcu/tree_nocb.h
index 08b5c0042979..3343e42685dc 100644
--- a/kernel/rcu/tree_nocb.h
+++ b/kernel/rcu/tree_nocb.h
@@ -1210,6 +1210,9 @@ static void rcu_spawn_one_nocb_kthread(int cpu)
"rcuo%c/%d", rcu_state.abbr, cpu);
if (WARN_ONCE(IS_ERR(t), "%s: Could not start rcuo CB kthread, OOM is now expected behavior\n", __func__))
return;
+
+ if (kthread_prio)
+ sched_setscheduler_nocheck(t, SCHED_FIFO, &sp);
WRITE_ONCE(rdp->nocb_cb_kthread, t);
WRITE_ONCE(rdp->nocb_gp_kthread, rdp_gp->nocb_gp_kthread);
}
--
2.32.0