linux-kernel - [PATCH v3 2/2] genirq/matrix: Avoid implicit tie-breaking by CPU iteration order

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Message-ID: <20260128031406.9473-3-zhanxusheng@xiaomi.com>
Date: Wed, 28 Jan 2026 11:14:06 +0800
From: Zhan Xusheng <zhanxusheng1024@...il.com>
To: Thomas Gleixner <tglx@...utronix.de>
Cc: linux-kernel@...r.kernel.org,
	linux-irq@...r.kernel.org,
	Zhan Xusheng <zhanxusheng@...omi.com>
Subject: [PATCH v3 2/2] genirq/matrix: Avoid implicit tie-breaking by CPU iteration order

matrix_find_best_cpu_managed() updates best_cpu even when two CPUs
have the same managed_allocated count. As a result, the final
selection implicitly depends on CPU iteration order.

Update the comparison to replace the current best CPU only when a
CPU has a strictly smaller managed_allocated value. This removes
the iteration-order-based tie-breaking for equal cases.

This patch intentionally changes the selection behavior.

Signed-off-by: Zhan Xusheng <zhanxusheng@...omi.com>
---
 kernel/irq/matrix.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/irq/matrix.c b/kernel/irq/matrix.c
index c363e918087c..ed4b1e44dc1e 100644
--- a/kernel/irq/matrix.c
+++ b/kernel/irq/matrix.c
@@ -171,7 +171,7 @@ static unsigned int matrix_find_best_cpu_managed(struct irq_matrix *m,
 		if (!cm->online)
 			continue;

-		if (cm->managed_allocated <= allocated) {
+		if (cm->managed_allocated < allocated) {
 			best_cpu = cpu;
 			allocated = cm->managed_allocated;
 		}
-- 
2.43.0