Hotplug CPU: don't check cpu_online after take_cpu_down

[linux-2.6-omap-h63xx.git] / kernel / cpu.c

diff --git a/kernel/cpu.c b/kernel/cpu.c
index b11f06dc149add3a29c072e2ec9356499dd9dbc1..53cf508f975a69bbcbdaad611a82a5415af4b113 100644 (file)
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -64,6 +64,8 @@ void __init cpu_hotplug_init(void)
        cpu_hotplug.refcount = 0;
 }
 
+cpumask_t cpu_active_map;
+
 #ifdef CONFIG_HOTPLUG_CPU
 
 void get_online_cpus(void)
@@ -214,7 +216,6 @@ static int __ref take_cpu_down(void *_param)
 static int __ref _cpu_down(unsigned int cpu, int tasks_frozen)
 {
        int err, nr_calls = 0;
-       struct task_struct *p;
        cpumask_t old_allowed, tmp;
        void *hcpu = (void *)(long)cpu;
        unsigned long mod = tasks_frozen ? CPU_TASKS_FROZEN : 0;
@@ -248,20 +249,16 @@ static int __ref _cpu_down(unsigned int cpu, int tasks_frozen)
        cpu_clear(cpu, tmp);
        set_cpus_allowed_ptr(current, &tmp);
 
-       p = __stop_machine_run(take_cpu_down, &tcd_param, cpu);
-
-       if (IS_ERR(p) || cpu_online(cpu)) {
+       err = __stop_machine_run(take_cpu_down, &tcd_param, cpu);
+       if (err) {
                /* CPU didn't die: tell everyone.  Can't complain. */
                if (raw_notifier_call_chain(&cpu_chain, CPU_DOWN_FAILED | mod,
                                            hcpu) == NOTIFY_BAD)
                        BUG();
 
-               if (IS_ERR(p)) {
-                       err = PTR_ERR(p);
-                       goto out_allowed;
-               }
-               goto out_thread;
+               goto out_allowed;
        }
+       BUG_ON(cpu_online(cpu));
 
        /* Wait for it to sleep (leaving idle task). */
        while (!idle_cpu(cpu))
@@ -277,12 +274,15 @@ static int __ref _cpu_down(unsigned int cpu, int tasks_frozen)
 
        check_for_tasks(cpu);
 
-out_thread:
-       err = kthread_stop(p);
 out_allowed:
        set_cpus_allowed_ptr(current, &old_allowed);
 out_release:
        cpu_hotplug_done();
+       if (!err) {
+               if (raw_notifier_call_chain(&cpu_chain, CPU_POST_DEAD | mod,
+                                           hcpu) == NOTIFY_BAD)
+                       BUG();
+       }
        return err;
 }
 
@@ -291,14 +291,34 @@ int __ref cpu_down(unsigned int cpu)
        int err = 0;
 
        cpu_maps_update_begin();
-       if (cpu_hotplug_disabled)
+
+       if (cpu_hotplug_disabled) {
                err = -EBUSY;
-       else
-               err = _cpu_down(cpu, 0);
+               goto out;
+       }
+
+       cpu_clear(cpu, cpu_active_map);
 
+       /*
+        * Make sure the all cpus did the reschedule and are not
+        * using stale version of the cpu_active_map.
+        * This is not strictly necessary becuase stop_machine()
+        * that we run down the line already provides the required
+        * synchronization. But it's really a side effect and we do not
+        * want to depend on the innards of the stop_machine here.
+        */
+       synchronize_sched();
+
+       err = _cpu_down(cpu, 0);
+
+       if (cpu_online(cpu))
+               cpu_set(cpu, cpu_active_map);
+
+out:
        cpu_maps_update_done();
        return err;
 }
+EXPORT_SYMBOL(cpu_down);
 #endif /*CONFIG_HOTPLUG_CPU*/
 
 /* Requires cpu_add_remove_lock to be held */
@@ -354,11 +374,18 @@ int __cpuinit cpu_up(unsigned int cpu)
        }
 
        cpu_maps_update_begin();
-       if (cpu_hotplug_disabled)
+
+       if (cpu_hotplug_disabled) {
                err = -EBUSY;
-       else
-               err = _cpu_up(cpu, 0);
+               goto out;
+       }
+
+       err = _cpu_up(cpu, 0);
 
+       if (cpu_online(cpu))
+               cpu_set(cpu, cpu_active_map);
+
+out:
        cpu_maps_update_done();
        return err;
 }
@@ -412,7 +439,7 @@ void __ref enable_nonboot_cpus(void)
                goto out;
 
        printk("Enabling non-boot CPUs ...\n");
-       for_each_cpu_mask(cpu, frozen_cpus) {
+       for_each_cpu_mask_nr(cpu, frozen_cpus) {
                error = _cpu_up(cpu, 1);
                if (!error) {
                        printk("CPU%d is up\n", cpu);