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Subject[tip: sched/core] sched/topology: Handle NUMA_NO_NODE in sched_numa_find_nth_cpu()
The following commit has been merged into the sched/core branch of tip:

Commit-ID: 9ecea9ae4d3127a09fb5dfcea87f248937a39ff5
Gitweb: https://git.kernel.org/tip/9ecea9ae4d3127a09fb5dfcea87f248937a39ff5
Author: Yury Norov <yury.norov@gmail.com>
AuthorDate: Sat, 19 Aug 2023 07:12:37 -07:00
Committer: Ingo Molnar <mingo@kernel.org>
CommitterDate: Fri, 15 Sep 2023 13:48:11 +02:00

sched/topology: 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@gmail.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Mel Gorman <mgorman@suse.de>
Link: https://lore.kernel.org/r/20230819141239.287290-6-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 423d089..a60ecf4 100644
--- a/kernel/sched/topology.c
+++ b/kernel/sched/topology.c
@@ -2126,6 +2126,9 @@ 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 a7fd02b..34335c1 100644
--- a/lib/cpumask.c
+++ b/lib/cpumask.c
@@ -146,9 +146,7 @@ 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;
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