linux-kernel - [PATCH] irq_work: Improve CPU Responsiveness in irq_work_sync with cond

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Message-ID:
 <SJ2P223MB10263844181902531B671FB6F7622@SJ2P223MB1026.NAMP223.PROD.OUTLOOK.COM>
Date: Wed, 18 Sep 2024 11:23:17 -0400
From: Steven Davis <goldside000@...look.com>
To: akpm@...ux-foundation.org
Cc: linux-kernel@...r.kernel.org,
	Steven Davis <goldside000@...look.com>
Subject: [PATCH] irq_work: Improve CPU Responsiveness in irq_work_sync with cond_resched()

Add cond_resched() to the busy-wait loop in irq_work_sync to improve
CPU responsiveness and prevent starvation of other tasks.

Previously, the busy-wait loop used cpu_relax() alone, which, while
reducing power consumption, could still lead to excessive CPU
monopolization in scenarios where IRQ work remains busy for extended
periods. By incorporating cond_resched(), the CPU is periodically yielded
to the scheduler, allowing other tasks to execute and enhancing overall
system responsiveness.

Signed-off-by: Steven Davis <goldside000@...look.com>
---
 kernel/irq_work.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/kernel/irq_work.c b/kernel/irq_work.c
index 2f4fb336dda1..bdc478979ee6 100644
--- a/kernel/irq_work.c
+++ b/kernel/irq_work.c
@@ -295,9 +295,17 @@ void irq_work_sync(struct irq_work *work)
 		return;
 	}

-	while (irq_work_is_busy(work))
+	int retry_count = 0;
+
+	while (irq_work_is_busy(work)) {
 		cpu_relax();
+
+	if (retry_count++ > 1000) {
+		cond_resched();
+		retry_count = 0;
+	}
 }
+
 EXPORT_SYMBOL_GPL(irq_work_sync);

 static void run_irq_workd(unsigned int cpu)
-- 
2.39.5