1 files changed, 156 insertions, 63 deletions

diff --git a/kernel/cpu.c b/kernel/cpu.c
index fe2b8d0bfe4c..32c96628463e 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -13,66 +13,66 @@
 #include <linux/module.h>
 #include <linux/kthread.h>
 #include <linux/stop_machine.h>
-#include <asm/semaphore.h>
+#include <linux/mutex.h>
 
 /* This protects CPUs going up and down... */
-static DECLARE_MUTEX(cpucontrol);
+static DEFINE_MUTEX(cpu_add_remove_lock);
+static DEFINE_MUTEX(cpu_bitmask_lock);
 
-static BLOCKING_NOTIFIER_HEAD(cpu_chain);
+static __cpuinitdata BLOCKING_NOTIFIER_HEAD(cpu_chain);
 
-#ifdef CONFIG_HOTPLUG_CPU
-static struct task_struct *lock_cpu_hotplug_owner;
-static int lock_cpu_hotplug_depth;
-
-static int __lock_cpu_hotplug(int interruptible)
-{
-        int ret = 0;
+/* If set, cpu_up and cpu_down will return -EBUSY and do nothing.
+ * Should always be manipulated under cpu_add_remove_lock
+ */
+static int cpu_hotplug_disabled;
 
-        if (lock_cpu_hotplug_owner != current) {
-                if (interruptible)
-                        ret = down_interruptible(&cpucontrol);
-                else
-                        down(&cpucontrol);
-        }
+#ifdef CONFIG_HOTPLUG_CPU
 
-        /*
-         * Set only if we succeed in locking
-         */
-        if (!ret) {
-                lock_cpu_hotplug_depth++;
-                lock_cpu_hotplug_owner = current;
-        }
-
-        return ret;
-}
+/* Crappy recursive lock-takers in cpufreq! Complain loudly about idiots */
+static struct task_struct *recursive;
+static int recursive_depth;
 
 void lock_cpu_hotplug(void)
 {
-        __lock_cpu_hotplug(0);
+        struct task_struct *tsk = current;
+
+        if (tsk == recursive) {
+                static int warnings = 10;
+                if (warnings) {
+                        printk(KERN_ERR "Lukewarm IQ detected in hotplug locking\n");
+                        WARN_ON(1);
+                        warnings--;
+                }
+                recursive_depth++;
+                return;
+        }
+        mutex_lock(&cpu_bitmask_lock);
+        recursive = tsk;
 }
 EXPORT_SYMBOL_GPL(lock_cpu_hotplug);
 
 void unlock_cpu_hotplug(void)
 {
-        if (--lock_cpu_hotplug_depth == 0) {
-                lock_cpu_hotplug_owner = NULL;
-                up(&cpucontrol);
+        WARN_ON(recursive != current);
+        if (recursive_depth) {
+                recursive_depth--;
+                return;
         }
+        mutex_unlock(&cpu_bitmask_lock);
+        recursive = NULL;
 }
 EXPORT_SYMBOL_GPL(unlock_cpu_hotplug);
 
-int lock_cpu_hotplug_interruptible(void)
-{
-        return __lock_cpu_hotplug(1);
-}
-EXPORT_SYMBOL_GPL(lock_cpu_hotplug_interruptible);
 #endif  /* CONFIG_HOTPLUG_CPU */
 
 /* Need to know about CPUs going up/down? */
-int register_cpu_notifier(struct notifier_block *nb)
+int __cpuinit register_cpu_notifier(struct notifier_block *nb)
 {
         return blocking_notifier_chain_register(&cpu_chain, nb);
 }
+
+#ifdef CONFIG_HOTPLUG_CPU
+
 EXPORT_SYMBOL(register_cpu_notifier);
 
 void unregister_cpu_notifier(struct notifier_block *nb)
@@ -81,7 +81,6 @@ void unregister_cpu_notifier(struct notifier_block *nb)
 }
 EXPORT_SYMBOL(unregister_cpu_notifier);
 
-#ifdef CONFIG_HOTPLUG_CPU
 static inline void check_for_tasks(int cpu)
 {
         struct task_struct *p;
@@ -114,32 +113,25 @@ static int take_cpu_down(void *unused)
         return 0;
 }
 
-int cpu_down(unsigned int cpu)
+/* Requires cpu_add_remove_lock to be held */
+static int _cpu_down(unsigned int cpu)
 {
         int err;
         struct task_struct *p;
         cpumask_t old_allowed, tmp;
 
-        if ((err = lock_cpu_hotplug_interruptible()) != 0)
-                return err;
+        if (num_online_cpus() == 1)
+                return -EBUSY;
 
-        if (num_online_cpus() == 1) {
-                err = -EBUSY;
-                goto out;
-        }
-
-        if (!cpu_online(cpu)) {
-                err = -EINVAL;
-                goto out;
-        }
+        if (!cpu_online(cpu))
+                return -EINVAL;
 
         err = blocking_notifier_call_chain(&cpu_chain, CPU_DOWN_PREPARE,
                                                 (void *)(long)cpu);
         if (err == NOTIFY_BAD) {
                 printk("%s: attempt to take down CPU %u failed\n",
                                 __FUNCTION__, cpu);
-                err = -EINVAL;
-                goto out;
+                return -EINVAL;
         }
 
         /* Ensure that we are not runnable on dying cpu */
@@ -148,7 +140,10 @@ int cpu_down(unsigned int cpu)
         cpu_clear(cpu, tmp);
         set_cpus_allowed(current, tmp);
 
+        mutex_lock(&cpu_bitmask_lock);
         p = __stop_machine_run(take_cpu_down, NULL, cpu);
+        mutex_unlock(&cpu_bitmask_lock);
+
         if (IS_ERR(p)) {
                 /* CPU didn't die: tell everyone.  Can't complain. */
                 if (blocking_notifier_call_chain(&cpu_chain, CPU_DOWN_FAILED,
@@ -184,24 +179,32 @@ out_thread:
         err = kthread_stop(p);
 out_allowed:
         set_cpus_allowed(current, old_allowed);
-out:
-        unlock_cpu_hotplug();
+        return err;
+}
+
+int cpu_down(unsigned int cpu)
+{
+        int err = 0;
+
+        mutex_lock(&cpu_add_remove_lock);
+        if (cpu_hotplug_disabled)
+                err = -EBUSY;
+        else
+                err = _cpu_down(cpu);
+
+        mutex_unlock(&cpu_add_remove_lock);
         return err;
 }
 #endif /*CONFIG_HOTPLUG_CPU*/
 
-int __devinit cpu_up(unsigned int cpu)
+/* Requires cpu_add_remove_lock to be held */
+static int __devinit _cpu_up(unsigned int cpu)
 {
         int ret;
         void *hcpu = (void *)(long)cpu;
 
-        if ((ret = lock_cpu_hotplug_interruptible()) != 0)
-                return ret;
-
-        if (cpu_online(cpu) || !cpu_present(cpu)) {
-                ret = -EINVAL;
-                goto out;
-        }
+        if (cpu_online(cpu) || !cpu_present(cpu))
+                return -EINVAL;
 
         ret = blocking_notifier_call_chain(&cpu_chain, CPU_UP_PREPARE, hcpu);
         if (ret == NOTIFY_BAD) {
@@ -212,7 +215,9 @@ int __devinit cpu_up(unsigned int cpu)
         }
 
         /* Arch-specific enabling code. */
+        mutex_lock(&cpu_bitmask_lock);
         ret = __cpu_up(cpu);
+        mutex_unlock(&cpu_bitmask_lock);
         if (ret != 0)
                 goto out_notify;
         BUG_ON(!cpu_online(cpu));
@@ -224,7 +229,95 @@ out_notify:
         if (ret != 0)
                 blocking_notifier_call_chain(&cpu_chain,
                                 CPU_UP_CANCELED, hcpu);
-out:
-        unlock_cpu_hotplug();
+
         return ret;
 }
+
+int __devinit cpu_up(unsigned int cpu)
+{
+        int err = 0;
+
+        mutex_lock(&cpu_add_remove_lock);
+        if (cpu_hotplug_disabled)
+                err = -EBUSY;
+        else
+                err = _cpu_up(cpu);
+
+        mutex_unlock(&cpu_add_remove_lock);
+        return err;
+}
+
+#ifdef CONFIG_SUSPEND_SMP
+static cpumask_t frozen_cpus;
+
+int disable_nonboot_cpus(void)
+{
+        int cpu, first_cpu, error;
+
+        mutex_lock(&cpu_add_remove_lock);
+        first_cpu = first_cpu(cpu_present_map);
+        if (!cpu_online(first_cpu)) {
+                error = _cpu_up(first_cpu);
+                if (error) {
+                        printk(KERN_ERR "Could not bring CPU%d up.\n",
+                                first_cpu);
+                        goto out;
+                }
+        }
+        error = set_cpus_allowed(current, cpumask_of_cpu(first_cpu));
+        if (error) {
+                printk(KERN_ERR "Could not run on CPU%d\n", first_cpu);
+                goto out;
+        }
+        /* We take down all of the non-boot CPUs in one shot to avoid races
+         * with the userspace trying to use the CPU hotplug at the same time
+         */
+        cpus_clear(frozen_cpus);
+        printk("Disabling non-boot CPUs ...\n");
+        for_each_online_cpu(cpu) {
+                if (cpu == first_cpu)
+                        continue;
+                error = _cpu_down(cpu);
+                if (!error) {
+                        cpu_set(cpu, frozen_cpus);
+                        printk("CPU%d is down\n", cpu);
+                } else {
+                        printk(KERN_ERR "Error taking CPU%d down: %d\n",
+                                cpu, error);
+                        break;
+                }
+        }
+        if (!error) {
+                BUG_ON(num_online_cpus() > 1);
+                /* Make sure the CPUs won't be enabled by someone else */
+                cpu_hotplug_disabled = 1;
+        } else {
+                printk(KERN_ERR "Non-boot CPUs are not disabled");
+        }
+out:
+        mutex_unlock(&cpu_add_remove_lock);
+        return error;
+}
+
+void enable_nonboot_cpus(void)
+{
+        int cpu, error;
+
+        /* Allow everyone to use the CPU hotplug again */
+        mutex_lock(&cpu_add_remove_lock);
+        cpu_hotplug_disabled = 0;
+        mutex_unlock(&cpu_add_remove_lock);
+
+        printk("Enabling non-boot CPUs ...\n");
+        for_each_cpu_mask(cpu, frozen_cpus) {
+                error = cpu_up(cpu);
+                if (!error) {
+                        printk("CPU%d is up\n", cpu);
+                        continue;
+                }
+                printk(KERN_WARNING "Error taking CPU%d up: %d\n",
+                        cpu, error);
+        }
+        cpus_clear(frozen_cpus);
+}
+#endif