From: Alison Chaiken <achaiken@aurora.tech>
To: tglx@linutronix.de
Cc: peterz@infradead.org, paulmck@kernel.org,
valentin.schneider@arm.com, frederic@kernel.org,
linux-kernel@vger.kernel.org, glenn@aurora.tech,
alison@she-devel.com, Alison Chaiken <achaiken@aurora.tech>
Subject: [PATCH 3/4] RCU: elevate priority of offloaded callback threads
Date: Tue, 11 Jan 2022 15:32:52 -0800 [thread overview]
Message-ID: <20220111233253.21692-4-achaiken@aurora.tech> (raw)
In-Reply-To: <20220111233253.21692-1-achaiken@aurora.tech>
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 <achaiken@aurora.tech>
---
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
next prev parent reply other threads:[~2022-01-13 2:15 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-11 23:32 [PATCH 0/5] handle kthread_prio kernel cmdline parameter consistently Alison Chaiken
2022-01-11 23:32 ` [PATCH 1/4] RCU: move kthread_prio bounds-check to a separate function Alison Chaiken
2022-01-11 23:32 ` [PATCH 2/4] RCU: make priority of grace-period thread consistent Alison Chaiken
2022-01-11 23:32 ` Alison Chaiken [this message]
2022-01-11 23:32 ` [PATCH 4/4] RCU: update documentation regarding kthread_prio cmdline parameter Alison Chaiken
2022-01-12 1:03 ` [PATCH 0/5] handle kthread_prio kernel cmdline parameter consistently Paul E. McKenney
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