[ARM SMP] Add hotplug CPU infrastructure
This patch adds the infrastructure to support hotplug CPU on ARM
platforms.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c
index b40915d..edb5a40 100644
--- a/arch/arm/kernel/smp.c
+++ b/arch/arm/kernel/smp.c
@@ -159,6 +159,91 @@
return ret;
}
+#ifdef CONFIG_HOTPLUG_CPU
+/*
+ * __cpu_disable runs on the processor to be shutdown.
+ */
+int __cpuexit __cpu_disable(void)
+{
+ unsigned int cpu = smp_processor_id();
+ struct task_struct *p;
+ int ret;
+
+ ret = mach_cpu_disable(cpu);
+ if (ret)
+ return ret;
+
+ /*
+ * Take this CPU offline. Once we clear this, we can't return,
+ * and we must not schedule until we're ready to give up the cpu.
+ */
+ cpu_clear(cpu, cpu_online_map);
+
+ /*
+ * OK - migrate IRQs away from this CPU
+ */
+ migrate_irqs();
+
+ /*
+ * Flush user cache and TLB mappings, and then remove this CPU
+ * from the vm mask set of all processes.
+ */
+ flush_cache_all();
+ local_flush_tlb_all();
+
+ read_lock(&tasklist_lock);
+ for_each_process(p) {
+ if (p->mm)
+ cpu_clear(cpu, p->mm->cpu_vm_mask);
+ }
+ read_unlock(&tasklist_lock);
+
+ return 0;
+}
+
+/*
+ * called on the thread which is asking for a CPU to be shutdown -
+ * waits until shutdown has completed, or it is timed out.
+ */
+void __cpuexit __cpu_die(unsigned int cpu)
+{
+ if (!platform_cpu_kill(cpu))
+ printk("CPU%u: unable to kill\n", cpu);
+}
+
+/*
+ * Called from the idle thread for the CPU which has been shutdown.
+ *
+ * Note that we disable IRQs here, but do not re-enable them
+ * before returning to the caller. This is also the behaviour
+ * of the other hotplug-cpu capable cores, so presumably coming
+ * out of idle fixes this.
+ */
+void __cpuexit cpu_die(void)
+{
+ unsigned int cpu = smp_processor_id();
+
+ local_irq_disable();
+ idle_task_exit();
+
+ /*
+ * actual CPU shutdown procedure is at least platform (if not
+ * CPU) specific
+ */
+ platform_cpu_die(cpu);
+
+ /*
+ * Do not return to the idle loop - jump back to the secondary
+ * cpu initialisation. There's some initialisation which needs
+ * to be repeated to undo the effects of taking the CPU offline.
+ */
+ __asm__("mov sp, %0\n"
+ " b secondary_start_kernel"
+ :
+ : "r" ((void *)current->thread_info + THREAD_SIZE - 8));
+}
+#endif /* CONFIG_HOTPLUG_CPU */
+
/*
* This is the secondary CPU boot entry. We're using this CPUs
* idle thread stack, but a set of temporary page tables.