[PATCH v2 5/6] sched: handle NUMA_NO_NODE in sched_numa_find_nth_cpu()

Yury Norov
2023-08-19T14:12:58Z

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@gmail.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