linux-kernel - [PATCH] rcu: Avoid strict QS reporting in NMI context

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Message-Id: <20220618022255.1697816-1-qiang1.zhang@intel.com>
Date:   Sat, 18 Jun 2022 10:22:55 +0800
From:   Zqiang <qiang1.zhang@...el.com>
To:     paulmck@...nel.org, frederic@...nel.org
Cc:     rcu@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] rcu: Avoid strict QS reporting in NMI context

Avoid invoke rcu_report_qs_rdp() in NMI handlers, in NMI handlers,
acquiring raw_spinlocks should be avoided, prevent NMI handlers
from blocking(spin) unnecessarily.

This commit make rcu_read_unlock_strict() early return when in
NMI context.

Signed-off-by: Zqiang <qiang1.zhang@...el.com>
---
 kernel/rcu/tree_plugin.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index dc78726b993f..e7a36e248a8a 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -821,7 +821,7 @@ void rcu_read_unlock_strict(void)
 {
 	struct rcu_data *rdp;
 
-	if (irqs_disabled() || preempt_count() || !rcu_state.gp_kthread)
+	if (in_nmi() || irqs_disabled() || preempt_count() || !rcu_state.gp_kthread)
 		return;
 	rdp = this_cpu_ptr(&rcu_data);
 	rdp->cpu_no_qs.b.norm = false;
-- 
2.25.1