x86/smp: Don't ever patch back to UP if we unplug cpus

[pandora-kernel.git] / kernel / cpu.c

diff --git a/kernel/cpu.c b/kernel/cpu.c
index 563f136..00251dd 100644 (file)
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -124,6 +124,27 @@ static void cpu_hotplug_done(void)
        mutex_unlock(&cpu_hotplug.lock);
 }
 
+/*
+ * Wait for currently running CPU hotplug operations to complete (if any) and
+ * disable future CPU hotplug (from sysfs). The 'cpu_add_remove_lock' protects
+ * the 'cpu_hotplug_disabled' flag. The same lock is also acquired by the
+ * hotplug path before performing hotplug operations. So acquiring that lock
+ * guarantees mutual exclusion from any currently running hotplug operations.
+ */
+void cpu_hotplug_disable(void)
+{
+       cpu_maps_update_begin();
+       cpu_hotplug_disabled = 1;
+       cpu_maps_update_done();
+}
+
+void cpu_hotplug_enable(void)
+{
+       cpu_maps_update_begin();
+       cpu_hotplug_disabled = 0;
+       cpu_maps_update_done();
+}
+
 #else /* #if CONFIG_HOTPLUG_CPU */
 static void cpu_hotplug_begin(void) {}
 static void cpu_hotplug_done(void) {}
@@ -155,12 +176,6 @@ static int cpu_notify(unsigned long val, void *v)
        return __cpu_notify(val, v, -1, NULL);
 }
 
-#ifdef CONFIG_HOTPLUG_CPU
-
-static void cpu_notify_nofail(unsigned long val, void *v)
-{
-       BUG_ON(cpu_notify(val, v));
-}
 EXPORT_SYMBOL(register_cpu_notifier);
 
 void __ref unregister_cpu_notifier(struct notifier_block *nb)
@@ -171,6 +186,13 @@ void __ref unregister_cpu_notifier(struct notifier_block *nb)
 }
 EXPORT_SYMBOL(unregister_cpu_notifier);
 
+#ifdef CONFIG_HOTPLUG_CPU
+
+static void cpu_notify_nofail(unsigned long val, void *v)
+{
+       BUG_ON(cpu_notify(val, v));
+}
+
 static inline void check_for_tasks(int cpu)
 {
        struct task_struct *p;
@@ -384,14 +406,6 @@ out:
 #ifdef CONFIG_PM_SLEEP_SMP
 static cpumask_var_t frozen_cpus;
 
-void __weak arch_disable_nonboot_cpus_begin(void)
-{
-}
-
-void __weak arch_disable_nonboot_cpus_end(void)
-{
-}
-
 int disable_nonboot_cpus(void)
 {
        int cpu, first_cpu, error = 0;
@@ -403,7 +417,6 @@ int disable_nonboot_cpus(void)
         * with the userspace trying to use the CPU hotplug at the same time
         */
        cpumask_clear(frozen_cpus);
-       arch_disable_nonboot_cpus_begin();
 
        printk("Disabling non-boot CPUs ...\n");
        for_each_online_cpu(cpu) {
@@ -419,8 +432,6 @@ int disable_nonboot_cpus(void)
                }
        }
 
-       arch_disable_nonboot_cpus_end();
-
        if (!error) {
                BUG_ON(num_online_cpus() > 1);
                /* Make sure the CPUs won't be enabled by someone else */
@@ -478,36 +489,6 @@ static int alloc_frozen_cpus(void)
 }
 core_initcall(alloc_frozen_cpus);
 
-/*
- * Prevent regular CPU hotplug from racing with the freezer, by disabling CPU
- * hotplug when tasks are about to be frozen. Also, don't allow the freezer
- * to continue until any currently running CPU hotplug operation gets
- * completed.
- * To modify the 'cpu_hotplug_disabled' flag, we need to acquire the
- * 'cpu_add_remove_lock'. And this same lock is also taken by the regular
- * CPU hotplug path and released only after it is complete. Thus, we
- * (and hence the freezer) will block here until any currently running CPU
- * hotplug operation gets completed.
- */
-void cpu_hotplug_disable_before_freeze(void)
-{
-       cpu_maps_update_begin();
-       cpu_hotplug_disabled = 1;
-       cpu_maps_update_done();
-}
-
-
-/*
- * When tasks have been thawed, re-enable regular CPU hotplug (which had been
- * disabled while beginning to freeze tasks).
- */
-void cpu_hotplug_enable_after_thaw(void)
-{
-       cpu_maps_update_begin();
-       cpu_hotplug_disabled = 0;
-       cpu_maps_update_done();
-}
-
 /*
  * When callbacks for CPU hotplug notifications are being executed, we must
  * ensure that the state of the system with respect to the tasks being frozen
@@ -527,12 +508,12 @@ cpu_hotplug_pm_callback(struct notifier_block *nb,
 
        case PM_SUSPEND_PREPARE:
        case PM_HIBERNATION_PREPARE:
-               cpu_hotplug_disable_before_freeze();
+               cpu_hotplug_disable();
                break;
 
        case PM_POST_SUSPEND:
        case PM_POST_HIBERNATION:
-               cpu_hotplug_enable_after_thaw();
+               cpu_hotplug_enable();
                break;
 
        default: