[PATCH] numa, mem-hotplug: Fix stack overflow in numa when seting kernel nodes to unhotpluggable.

[Tang Chen]

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.

Reported-by: Dave Jones <davej@xxxxxxxxxx>
Signed-off-by: Tang Chen <tangchen@xxxxxxxxxxxxxx>
Tested-by: Gu Zheng <guz.fnst@xxxxxxxxxxxxxx>
---
 arch/x86/mm/numa.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/mm/numa.c b/arch/x86/mm/numa.c
index 81b2750..ebefeb7 100644
--- 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;
 
-- 
1.7.11.7

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