1 files changed, 46 insertions, 0 deletions

diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
index 8d4214afc21d..c4f420c5fc1b 100644
--- a/arch/powerpc/kernel/smp.c
+++ b/arch/powerpc/kernel/smp.c
@@ -417,6 +417,45 @@ int generic_check_cpu_restart(unsigned int cpu)
 {
         return per_cpu(cpu_state, cpu) == CPU_UP_PREPARE;
 }
+
+static atomic_t secondary_inhibit_count;
+
+/*
+ * Don't allow secondary CPU threads to come online
+ */
+void inhibit_secondary_onlining(void)
+{
+        /*
+         * This makes secondary_inhibit_count stable during cpu
+         * online/offline operations.
+         */
+        get_online_cpus();
+
+        atomic_inc(&secondary_inhibit_count);
+        put_online_cpus();
+}
+EXPORT_SYMBOL_GPL(inhibit_secondary_onlining);
+
+/*
+ * Allow secondary CPU threads to come online again
+ */
+void uninhibit_secondary_onlining(void)
+{
+        get_online_cpus();
+        atomic_dec(&secondary_inhibit_count);
+        put_online_cpus();
+}
+EXPORT_SYMBOL_GPL(uninhibit_secondary_onlining);
+
+static int secondaries_inhibited(void)
+{
+        return atomic_read(&secondary_inhibit_count);
+}
+
+#else /* HOTPLUG_CPU */
+
+#define secondaries_inhibited()         0
+
 #endif
 
 static void cpu_idle_thread_init(unsigned int cpu, struct task_struct *idle)
@@ -435,6 +474,13 @@ int __cpuinit __cpu_up(unsigned int cpu, struct task_struct *tidle)
 {
         int rc, c;
 
+        /*
+         * Don't allow secondary threads to come online if inhibited
+         */
+        if (threads_per_core > 1 && secondaries_inhibited() &&
+            cpu % threads_per_core != 0)
+                return -EBUSY;
+
         if (smp_ops == NULL ||
             (smp_ops->cpu_bootable && !smp_ops->cpu_bootable(cpu)))
                 return -EINVAL;