On Mon, 8 Oct 2012, Tang Chen wrote:
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 66b36ab..e76dce9 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -1263,18 +1263,24 @@ EXPORT_SYMBOL_GPL(kick_process);
> */
> static int select_fallback_rq(int cpu, struct task_struct *p)
> {
> - const struct cpumask *nodemask = cpumask_of_node(cpu_to_node(cpu));
> + int nid = cpu_to_node(cpu);
> + const struct cpumask *nodemask = NULL;
> enum { cpuset, possible, fail } state = cpuset;
> int dest_cpu;
>
> - /* Look for allowed, online CPU in same node. */
> - for_each_cpu(dest_cpu, nodemask) {
> - if (!cpu_online(dest_cpu))
> - continue;
> - if (!cpu_active(dest_cpu))
> - continue;
> - if (cpumask_test_cpu(dest_cpu, tsk_cpus_allowed(p)))
> - return dest_cpu;
> + /* If the cpu has been offlined, its nid was set to -1. */
> + if (nid != -1) {
NUMA_NO_NODE.
Eek, the nid shouldn't be -1 yet, though, for cpu hotplug since this
should be called at CPU_DYING level and migrate_tasks() still sees a valid
cpu.
On x86, cpumask_of_node() is always guaranteed to return a valid cpumask
after boot so presumably this is a problem in some non-x86 arch code and
isn't actually a sched problem.
> + nodemask = cpumask_of_node(nid);
> +
> + /* Look for allowed, online CPU in same node. */
> + for_each_cpu(dest_cpu, nodemask) {
> + if (!cpu_online(dest_cpu))
> + continue;
> + if (!cpu_active(dest_cpu))
> + continue;
> + if (cpumask_test_cpu(dest_cpu, tsk_cpus_allowed(p)))
> + return dest_cpu;
> + }
> }
>
> for (;;) {
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