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 12b7458..00251dd 100644 (file)
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -10,11 +10,12 @@
 #include <linux/sched.h>
 #include <linux/unistd.h>
 #include <linux/cpu.h>
-#include <linux/module.h>
+#include <linux/export.h>
 #include <linux/kthread.h>
 #include <linux/stop_machine.h>
 #include <linux/mutex.h>
 #include <linux/gfp.h>
+#include <linux/suspend.h>
 
 #ifdef CONFIG_SMP
 /* Serializes the updates to cpu_online_mask, cpu_present_mask */
@@ -123,6 +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) {}
@@ -154,12 +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)
@@ -170,6 +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;
@@ -383,14 +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;
@@ -402,7 +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) {
@@ -418,8 +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 */
@@ -476,6 +488,49 @@ static int alloc_frozen_cpus(void)
        return 0;
 }
 core_initcall(alloc_frozen_cpus);
+
+/*
+ * 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
+ * or not, as reported by the notification, remains unchanged *throughout the
+ * duration* of the execution of the callbacks.
+ * Hence we need to prevent the freezer from racing with regular CPU hotplug.
+ *
+ * This synchronization is implemented by mutually excluding regular CPU
+ * hotplug and Suspend/Hibernate call paths by hooking onto the Suspend/
+ * Hibernate notifications.
+ */
+static int
+cpu_hotplug_pm_callback(struct notifier_block *nb,
+                       unsigned long action, void *ptr)
+{
+       switch (action) {
+
+       case PM_SUSPEND_PREPARE:
+       case PM_HIBERNATION_PREPARE:
+               cpu_hotplug_disable();
+               break;
+
+       case PM_POST_SUSPEND:
+       case PM_POST_HIBERNATION:
+               cpu_hotplug_enable();
+               break;
+
+       default:
+               return NOTIFY_DONE;
+       }
+
+       return NOTIFY_OK;
+}
+
+
+int cpu_hotplug_pm_sync_init(void)
+{
+       pm_notifier(cpu_hotplug_pm_callback, 0);
+       return 0;
+}
+core_initcall(cpu_hotplug_pm_sync_init);
+
 #endif /* CONFIG_PM_SLEEP_SMP */
 
 /**