In current kernel code, we only call node_set_state(cpu_to_node(cpu),
N_CPU) when a cpu is hot plugged. But we do not set the node state for
N_CPU when the cpus are brought online during boot.
So this could lead to failure when we check to see
if a node contains cpu with node_state(node_id, N_CPU).
One use case is in the node_reclaime function:
/*
* Only run node reclaim on the local node or on nodes that do
* not
* have associated processors. This will favor the local
* processor
* over remote processors and spread off node memory allocations
* as wide as possible.
*/
if (node_state(pgdat->node_id, N_CPU) && pgdat->node_id !=
numa_node_id())
return NODE_RECLAIM_NOSCAN;
I instrumented the kernel to call this function after boot and it
always returns 0 on a x86 desktop machine until I apply
the attached patch.
static int num_cpu_node(void)
{
int i, nr_cpu_nodes = 0;
for_each_node(i) {
if (node_state(i, N_CPU))
++ nr_cpu_nodes;
}
return nr_cpu_nodes;
}
I have not tested other architectues but they are likely
to have similar issue.
Signed-off-by: Tim Chen <[email protected]>
---
arch/x86/kernel/smpboot.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index d8f7d01..04c0574 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -259,6 +259,7 @@ static void notrace start_secondary(void *unused)
lock_vector_lock();
setup_vector_irq(smp_processor_id());
set_cpu_online(smp_processor_id(), true);
+ node_set_state(cpu_to_node(smp_processor_id()), N_CPU);
unlock_vector_lock();
cpu_set_state_online(smp_processor_id());
x86_platform.nmi_init();
--
2.5.5
