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From:   Zqiang <qiang1.zhang@intel.com>
To:     paulmck@kernel.org, frederic@kernel.org
Cc:     rcu@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH] rcu: Put the irq work into hard interrupt context for execution
Date:   Wed, 30 Mar 2022 14:00:12 +0800
Message-Id: <20220330060012.2470054-1-qiang1.zhang@intel.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

In PREEMPT_RT kernel, if irq work flags is not set, it will be
executed in per-CPU irq_work kthreads. set IRQ_WORK_HARD_IRQ flags
to irq work, put it in the context of hard interrupt execution,
accelerate scheduler to re-evaluate.

Signed-off-by: Zqiang <qiang1.zhang@intel.com>
---
 kernel/rcu/tree.c        | 2 +-
 kernel/rcu/tree_plugin.h | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index e2ffbeceba69..a69587773a85 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -678,7 +678,7 @@ static void late_wakeup_func(struct irq_work *work)
 }
 
 static DEFINE_PER_CPU(struct irq_work, late_wakeup_work) =
-	IRQ_WORK_INIT(late_wakeup_func);
+	IRQ_WORK_INIT_HARD(late_wakeup_func);
 
 /*
  * If either:
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 3037c2536e1f..cf7bd28af8ef 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -661,7 +661,7 @@ static void rcu_read_unlock_special(struct task_struct *t)
 			    expboost && !rdp->defer_qs_iw_pending && cpu_online(rdp->cpu)) {
 				// Get scheduler to re-evaluate and call hooks.
 				// If !IRQ_WORK, FQS scan will eventually IPI.
-				init_irq_work(&rdp->defer_qs_iw, rcu_preempt_deferred_qs_handler);
+				rdp->defer_qs_iw = IRQ_WORK_INIT_HARD(rcu_preempt_deferred_qs_handler);
 				rdp->defer_qs_iw_pending = true;
 				irq_work_queue_on(&rdp->defer_qs_iw, rdp->cpu);
 			}
-- 
2.25.1