linux-kernel - [PATCH] irq: consider cpus on nodes are unbalanced

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Message-Id: <20211029082730.6728-1-yamamoto.rei@jp.fujitsu.com>
Date:   Fri, 29 Oct 2021 17:27:30 +0900
From:   Rei Yamamoto <yamamoto.rei@...fujitsu.com>
To:     tglx@...utronix.de
Cc:     linux-kernel@...r.kernel.org, yamamoto.rei@...fujitsu.com
Subject: [PATCH] irq: consider cpus on nodes are unbalanced

If cpus on a node are offline at boot time, there are
difference in the number of nodes between when building affinity
masks for present cpus and when building affinity masks for possible
cpus. This patch fixes 2 problems caused by the difference of the
number of nodes:

 - If some unused vectors remain after building masks for present cpus,
   remained vectors are assigned for building masks for possible cpus.
   Therefore "numvecs <= nodes" condition must be
   "vecs_to_assign <= nodes_to_assign". Fix this problem by making this
   condition appropriate.

 - The routine of "numvecs <= nodes" condition can overwrite bits of
   masks for present cpus in building masks for possible cpus. Fix this
   problem by making CPU bits, which is not target, not changing.

Signed-off-by: Rei Yamamoto <yamamoto.rei@...fujitsu.com>
---
 kernel/irq/affinity.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/kernel/irq/affinity.c b/kernel/irq/affinity.c
index f7ff8919dc9b..1cdf89e5e2fb 100644
--- a/kernel/irq/affinity.c
+++ b/kernel/irq/affinity.c
@@ -267,10 +267,16 @@ static int __irq_build_affinity_masks(unsigned int startvec,
 	 * If the number of nodes in the mask is greater than or equal the
 	 * number of vectors we just spread the vectors across the nodes.
 	 */
-	if (numvecs <= nodes) {
+	if (numvecs - (curvec - firstvec) <= nodes) {
 		for_each_node_mask(n, nodemsk) {
+			unsigned int ncpus;
+
+			cpumask_and(nmsk, cpu_mask, node_to_cpumask[n]);
+			ncpus = cpumask_weight(nmsk);
+			if (!ncpus)
+				continue;
 			cpumask_or(&masks[curvec].mask, &masks[curvec].mask,
-				   node_to_cpumask[n]);
+				   nmsk);
 			if (++curvec == last_affv)
 				curvec = firstvec;
 		}
-- 
2.27.0