[PATCH] x86_64: tight online check in setup_per_cpu_areas

[PATCH] x86_64: tight online check in setup_per_cpu_areas

[Yinghai Lu]

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[PATCH] x86_64: tight online check in setup_per_cpu_areas

when numa disabled got compile warning:
arch/x86/kernel/setup64.c: In function ‘setup_per_cpu_areas’:
arch/x86/kernel/setup64.c:147: warning: the address of ‘contig_page_data’ will always evaluate as ‘true’

it seems we missed checking if the node is online before we try to refer
 NODE_DATA.
so fix it

Signed-off-by: Yinghai Lu <yhlu.kernel@gmail.com>

Index: linux-2.6/arch/x86/kernel/setup64.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/setup64.c
+++ linux-2.6/arch/x86/kernel/setup64.c
@@ -143,14 +143,16 @@ void __init setup_per_cpu_areas(void)
 	printk(KERN_INFO "PERCPU: Allocating %lu bytes of per cpu data\n", size);
 	for_each_cpu_mask (i, cpu_possible_map) {
 		char *ptr;
+#ifndef CONFIG_NEED_MULTIPLE_NODES
+		ptr = alloc_bootmem_pages(size);
+#else
+		int node = early_cpu_to_node(i);
 
-		if (!NODE_DATA(early_cpu_to_node(i))) {
-			printk("cpu with no node %d, num_online_nodes %d\n",
-			       i, num_online_nodes());
+		if (!node_online(node) || !NODE_DATA(node))
 			ptr = alloc_bootmem_pages(size);
-		} else { 
-			ptr = alloc_bootmem_pages_node(NODE_DATA(early_cpu_to_node(i)), size);
-		}
+		else
+			ptr = alloc_bootmem_pages_node(NODE_DATA(node), size);
+#endif
 		if (!ptr)
 			panic("Cannot allocate cpu data for CPU %d\n", i);
 		cpu_pda(i)->data_offset = ptr - __per_cpu_start;

Re: [PATCH] x86_64: tight online check in setup_per_cpu_areas

[Ingo Molnar]

* Yinghai Lu <yhlu.kernel@gmail.com> wrote:

> [PATCH] x86_64: tight online check in setup_per_cpu_areas
> 
> when numa disabled got compile warning:
> arch/x86/kernel/setup64.c: In function ???setup_per_cpu_areas???:
> arch/x86/kernel/setup64.c:147: warning: the address of ???contig_page_data??? will always evaluate as ???true???
> 
> it seems we missed checking if the node is online before we try to 
> refer NODE_DATA. so fix it

thanks, applied.

> +#ifndef CONFIG_NEED_MULTIPLE_NODES
> +		ptr = alloc_bootmem_pages(size);
> +#else
> +		int node = early_cpu_to_node(i);
>  
> +		if (!node_online(node) || !NODE_DATA(node))
>  			ptr = alloc_bootmem_pages(size);
> +		else
> +			ptr = alloc_bootmem_pages_node(NODE_DATA(node), size);
> +#endif

i'm wondering, shouldnt there just be a single facility for this mode of 
allocation, instead of this #ifdef and branch maze?

	Ingo