On 2016/8/26 23:49, Will Deacon wrote:

On Wed, Aug 24, 2016 at 03:44:51PM +0800, Zhen Lei wrote:

quoted

1. Currently only cpu0 set on cpu_possible_mask and percpu areas have not
   been initialized.

This description refer to below:
-	for_each_possible_cpu(cpu)
-		set_cpu_numa_node(cpu, NUMA_NO_NODE);

1. When the above code is executed, only the bit of cpu0 was set on cpu_possible_mask.
   So that, only set_cpu_numa_node(0, NUMA_NO_NODE); will be executed.
2. set_cpu_numa_node will access percpu variable numa_node, but setup_per_cpu_areas is
   called after current time. Without the first problem, it will lead kernel crash.

I changed the title of this patch in v7, the original is "remove some useless code".
I think I should separate this into a new patch.

quoted

2. No reason to limit cpu0 must belongs to node0.

Whilst I suspect you're using enumerated lists in order to try to make
things clearer, I'm having a really hard time understanding the commit
messages you have in this series. It's actually much better if you
structure them as concise paragraphs explaining:

  - What is the problem that you're fixing?

  - How does that problem manifest?

  - How does the patch fix it?

As far as I can see, this patch just removes a bunch of code with no
explanation as to why it's not required or any problems caused by
keeping it around.

Will

quoted

Signed-off-by: Zhen Lei <redacted>
---
 arch/arm64/mm/numa.c | 12 ++----------
 1 file changed, 2 insertions(+), 10 deletions(-)

diff --git a/arch/arm64/mm/numa.c b/arch/arm64/mm/numa.c
index 114180f..07a1978 100644
--- a/arch/arm64/mm/numa.c
+++ b/arch/arm64/mm/numa.c

@@ -94,7 +94,6 @@ void numa_clear_node(unsigned int cpu)
  */
 static void __init setup_node_to_cpumask_map(void)
 {
-	unsigned int cpu;
 	int node;

 	/* setup nr_node_ids if not done yet */

@@ -107,9 +106,6 @@ static void __init setup_node_to_cpumask_map(void)
 		cpumask_clear(node_to_cpumask_map[node]);
 	}

-	for_each_possible_cpu(cpu)
-		set_cpu_numa_node(cpu, NUMA_NO_NODE);
-
 	/* cpumask_of_node() will now work */
 	pr_debug("Node to cpumask map for %d nodes\n", nr_node_ids);
 }

@@ -119,13 +115,13 @@ static void __init setup_node_to_cpumask_map(void)
  */
 void numa_store_cpu_info(unsigned int cpu)
 {
-	map_cpu_to_node(cpu, numa_off ? 0 : cpu_to_node_map[cpu]);
+	map_cpu_to_node(cpu, cpu_to_node_map[cpu]);
 }

 void __init early_map_cpu_to_node(unsigned int cpu, int nid)
 {
 	/* fallback to node 0 */
-	if (nid < 0 || nid >= MAX_NUMNODES)
+	if (nid < 0 || nid >= MAX_NUMNODES || numa_off)
 		nid = 0;

After the below code have been removed, we should make the corresponding adjustment.
otherwise, kernel will be crashed if "numa=off" was set in bootargs.

quoted

 	cpu_to_node_map[cpu] = nid;

@@ -375,10 +371,6 @@ static int __init numa_init(int (*init_func)(void))

 	setup_node_to_cpumask_map();

-	/* init boot processor */
-	cpu_to_node_map[0] = 0;
-	map_cpu_to_node(0, 0);

These code limit cpu0 must belong to node0, but our current implementation deesn't
have this limitation.

quoted

-
 	return 0;
 }

--
2.5.0

.