[PATCH v5 2/3] sched/topology: Introduce for_each_numa_hop_mask()

Valentin Schneider
2022-10-21T12:20:05Z

The recently introduced sched_numa_hop_mask() exposes cpumasks of CPUs
reachable within a given distance budget, wrap the logic for iterating over
all (distance, mask) values inside an iterator macro.

Signed-off-by: Valentin Schneider <vschneid@redhat.com>
---
include/linux/topology.h | 30 +++++++++++++++++++++++++-----
1 file changed, 25 insertions(+), 5 deletions(-)

diff --git a/include/linux/topology.h b/include/linux/topology.h
index 3e91ae6d0ad58..8185e12ec1ccc 100644
--- a/include/linux/topology.h
+++ b/include/linux/topology.h
@@ -246,16 +246,36 @@ static inline const struct cpumask *cpu_cpu_mask(int cpu)
}

#ifdef CONFIG_NUMA
-extern const struct cpumask *sched_numa_hop_mask(int node, int hops);
+extern const struct cpumask *sched_numa_hop_mask(unsigned int node, unsigned int hops);
#else
-static inline const struct cpumask *sched_numa_hop_mask(int node, int hops)
+static inline const struct cpumask *
+sched_numa_hop_mask(unsigned int node, unsigned int hops)
{
- if (node == NUMA_NO_NODE && !hops)
- return cpu_online_mask;
-
return ERR_PTR(-EOPNOTSUPP);
}
#endif /* CONFIG_NUMA */

+/**
+ * for_each_numa_hop_mask - iterate over cpumasks of increasing NUMA distance
+ * from a given node.
+ * @mask: the iteration variable.
+ * @node: the NUMA node to start the search from.
+ *
+ * Requires rcu_lock to be held.
+ *
+ * Yields cpu_online_mask for @node == NUMA_NO_NODE.
+ */
+#define for_each_numa_hop_mask(mask, node) \
+ for (unsigned int __hops = 0; \
+ /* \
+ * Unsightly trickery required as we can't both initialize \
+ * @mask and declare __hops in for()'s first clause \
+ */ \
+ mask = __hops > 0 ? mask : \
+ node == NUMA_NO_NODE ? \
+ cpu_online_mask : sched_numa_hop_mask(node, 0), \
+ !IS_ERR_OR_NULL(mask); \
+ __hops++, \
+ mask = sched_numa_hop_mask(node, __hops))

#endif /* _LINUX_TOPOLOGY_H */
--
2.31.1