Re: [PATCH RFC 11/22] drivers: base: remove unnecessary call to register_cpu_under_node()

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On 11/7/23 20:30, Russell King (Oracle) wrote:
Since "drivers: base: Move cpu_dev_init() after node_dev_init()", we
can remove some redundant code.

node_dev_init() will walk through the nodes calling register_one_node()
on each. This will trickle down to __register_one_node() which walks
all present CPUs, calling register_cpu_under_node() on each.

register_cpu_under_node() will call get_cpu_device(cpu) for each, which
will return NULL until the CPU is registered using register_cpu(). This
now happens _after_ node_dev_init().

Therefore, calling register_cpu_under_node() from __register_one_node()
becomes a no-op, and can be removed.

Signed-off-by: Russell King (Oracle) <rmk+kernel@xxxxxxxxxxxxxxx>
---
  drivers/base/node.c | 7 -------
  1 file changed, 7 deletions(-)


__register_one_node() can be called in memory hot add path either. In that path,
a new NUMA node can be presented and becomes online. Does this become a problem
after the logic of associating CPU with newly added NUMA node?

Thanks,
Gavin

diff --git a/drivers/base/node.c b/drivers/base/node.c
index 493d533f8375..4d5ac7cf8757 100644
--- a/drivers/base/node.c
+++ b/drivers/base/node.c
@@ -867,7 +867,6 @@ void register_memory_blocks_under_node(int nid, unsigned long start_pfn,
  int __register_one_node(int nid)
  {
  	int error;
-	int cpu;
node_devices[nid] = kzalloc(sizeof(struct node), GFP_KERNEL);
  	if (!node_devices[nid])
@@ -875,12 +874,6 @@ int __register_one_node(int nid)
error = register_node(node_devices[nid], nid); - /* link cpu under this node */
-	for_each_present_cpu(cpu) {
-		if (cpu_to_node(cpu) == nid)
-			register_cpu_under_node(cpu, nid);
-	}
-
  	INIT_LIST_HEAD(&node_devices[nid]->access_list);
  	node_init_caches(nid);





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