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SubjectRe: [PATCH] numa, mem-hotplug: Fix stack overflow in numa when seting kernel nodes to unhotpluggable.
On Thu, 23 Jan 2014 13:49:28 +0800 Tang Chen <tangchen@cn.fujitsu.com> wrote:

> Dave found that the kernel will hang during boot. This is because
> the nodemask_t type stack variable numa_kernel_nodes is large enough
> to overflow the stack.
>
> This doesn't always happen. According to Dave, this happened once
> in about five boots. The backtrace is like the following:
>
> dump_stack
> panic
> ? numa_clear_kernel_node_hotplug
> __stack_chk_fail
> numa_clear_kernel_node_hotplug
> ? memblock_search_pfn_nid
> ? __early_pfn_to_nid
> numa_init
> x86_numa_init
> initmem_init
> setup_arch
> start_kernel
>
> This patch fix this problem by defining numa_kernel_nodes as a
> static global variable in __initdata area.
>
> ...
>
> --- a/arch/x86/mm/numa.c
> +++ b/arch/x86/mm/numa.c
> @@ -562,10 +562,10 @@ static void __init numa_init_array(void)
> }
> }
>
> +static nodemask_t numa_kernel_nodes __initdata;
> static void __init numa_clear_kernel_node_hotplug(void)
> {
> int i, nid;
> - nodemask_t numa_kernel_nodes;
> unsigned long start, end;
> struct memblock_type *type = &memblock.reserved;

Seems odd. The maximum size of a nodemask_t is 128 bytes, isn't it?
If so, what the heck have we done in there to consume so much stack?



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