linux-kernel - [PATCH v2 5/6] sched: handle NUMA_NO_NODE in sched_numa_find_nth

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Message-Id: <20230819141239.287290-6-yury.norov@gmail.com>
Date:   Sat, 19 Aug 2023 07:12:37 -0700
From:   Yury Norov <yury.norov@...il.com>
To:     linux-kernel@...r.kernel.org, linux-mm@...ck.org
Cc:     Yury Norov <yury.norov@...il.com>, Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Ben Segall <bsegall@...gle.com>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Jacob Keller <jacob.e.keller@...el.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Mel Gorman <mgorman@...e.de>,
        Steven Rostedt <rostedt@...dmis.org>,
        Tariq Toukan <tariqt@...dia.com>,
        Valentin Schneider <vschneid@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        shiju.jose@...wei.com, jonathan.cameron@...wei.com,
        prime.zeng@...wei.com, linuxarm@...wei.com,
        yangyicong@...ilicon.com,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>
Subject: [PATCH v2 5/6] sched: handle NUMA_NO_NODE in sched_numa_find_nth_cpu()

sched_numa_find_nth_cpu() doesn't handle NUMA_NO_NODE properly, and
may crash kernel if passed with it. On the other hand, the only user
of sched_numa_find_nth_cpu() has to check NUMA_NO_NODE case explicitly.

It would be easier for users if this logic will get moved into
sched_numa_find_nth_cpu().

Signed-off-by: Yury Norov <yury.norov@...il.com>
---
 kernel/sched/topology.c | 3 +++
 lib/cpumask.c           | 4 +---
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
index c6e89afa0d65..bc6802700103 100644
--- a/kernel/sched/topology.c
+++ b/kernel/sched/topology.c
@@ -2117,6 +2117,9 @@ int sched_numa_find_nth_cpu(const struct cpumask *cpus, int cpu, int node)
 	struct cpumask ***hop_masks;
 	int hop, ret = nr_cpu_ids;
 
+	if (node == NUMA_NO_NODE)
+		return cpumask_nth_and(cpu, cpus, cpu_online_mask);
+
 	rcu_read_lock();
 
 	/* CPU-less node entries are uninitialized in sched_domains_numa_masks */
diff --git a/lib/cpumask.c b/lib/cpumask.c
index 19277c6d551f..e77ee9d46f71 100644
--- a/lib/cpumask.c
+++ b/lib/cpumask.c
@@ -147,9 +147,7 @@ unsigned int cpumask_local_spread(unsigned int i, int node)
 	/* Wrap: we always want a cpu. */
 	i %= num_online_cpus();
 
-	cpu = (node == NUMA_NO_NODE) ?
-		cpumask_nth(i, cpu_online_mask) :
-		sched_numa_find_nth_cpu(cpu_online_mask, i, node);
+	cpu = sched_numa_find_nth_cpu(cpu_online_mask, i, node);
 
 	WARN_ON(cpu >= nr_cpu_ids);
 	return cpu;
-- 
2.39.2