cpu/hotplug: Split out cpu down functions

Split cpu_down in separate functions in preparation for state machine
conversion.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-arch@vger.kernel.org
Cc: Rik van Riel <riel@redhat.com>
Cc: Rafael Wysocki <rafael.j.wysocki@intel.com>
Cc: "Srivatsa S. Bhat" <srivatsa@mit.edu>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Sebastian Siewior <bigeasy@linutronix.de>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul Turner <pjt@google.com>
Link: http://lkml.kernel.org/r/20160226182340.511796562@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

diff --git a/kernel/cpu.c b/kernel/cpu.c
index 15a413639abc9da8483d501b03264aeaa7131fcf..0b5d2596f3ec6c55cc345b11463acf1d1e430438 100644 (file)
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -266,11 +266,6 @@ static int bringup_cpu(unsigned int cpu)
 }
 
 #ifdef CONFIG_HOTPLUG_CPU
-
-static void cpu_notify_nofail(unsigned long val, unsigned int cpu)
-{
-       BUG_ON(cpu_notify(val, cpu));
-}
 EXPORT_SYMBOL(register_cpu_notifier);
 EXPORT_SYMBOL(__register_cpu_notifier);
 
@@ -353,6 +348,25 @@ static inline void check_for_tasks(int dead_cpu)
        read_unlock(&tasklist_lock);
 }
 
+static void cpu_notify_nofail(unsigned long val, unsigned int cpu)
+{
+       BUG_ON(cpu_notify(val, cpu));
+}
+
+static int notify_down_prepare(unsigned int cpu)
+{
+       int err, nr_calls = 0;
+
+       err = __cpu_notify(CPU_DOWN_PREPARE, cpu, -1, &nr_calls);
+       if (err) {
+               nr_calls--;
+               __cpu_notify(CPU_DOWN_FAILED, cpu, nr_calls, NULL);
+               pr_warn("%s: attempt to take down CPU %u failed\n",
+                               __func__, cpu);
+       }
+       return err;
+}
+
 /* Take this CPU down. */
 static int take_cpu_down(void *_param)
 {
@@ -371,29 +385,9 @@ static int take_cpu_down(void *_param)
        return 0;
 }
 
-/* Requires cpu_add_remove_lock to be held */
-static int _cpu_down(unsigned int cpu, int tasks_frozen)
+static int takedown_cpu(unsigned int cpu)
 {
-       int err, nr_calls = 0;
-
-       if (num_online_cpus() == 1)
-               return -EBUSY;
-
-       if (!cpu_online(cpu))
-               return -EINVAL;
-
-       cpu_hotplug_begin();
-
-       cpuhp_tasks_frozen = tasks_frozen;
-
-       err = __cpu_notify(CPU_DOWN_PREPARE, cpu, -1, &nr_calls);
-       if (err) {
-               nr_calls--;
-               __cpu_notify(CPU_DOWN_FAILED, cpu, nr_calls, NULL);
-               pr_warn("%s: attempt to take down CPU %u failed\n",
-                       __func__, cpu);
-               goto out_release;
-       }
+       int err;
 
        /*
         * By now we've cleared cpu_active_mask, wait for all preempt-disabled
@@ -426,7 +420,7 @@ static int _cpu_down(unsigned int cpu, int tasks_frozen)
                /* CPU didn't die: tell everyone.  Can't complain. */
                cpu_notify_nofail(CPU_DOWN_FAILED, cpu);
                irq_unlock_sparse();
-               goto out_release;
+               return err;
        }
        BUG_ON(cpu_online(cpu));
 
@@ -449,11 +443,40 @@ static int _cpu_down(unsigned int cpu, int tasks_frozen)
        /* This actually kills the CPU. */
        __cpu_die(cpu);
 
-       /* CPU is completely dead: tell everyone.  Too late to complain. */
        tick_cleanup_dead_cpu(cpu);
-       cpu_notify_nofail(CPU_DEAD, cpu);
+       return 0;
+}
 
+static int notify_dead(unsigned int cpu)
+{
+       cpu_notify_nofail(CPU_DEAD, cpu);
        check_for_tasks(cpu);
+       return 0;
+}
+
+/* Requires cpu_add_remove_lock to be held */
+static int __ref _cpu_down(unsigned int cpu, int tasks_frozen)
+{
+       int err;
+
+       if (num_online_cpus() == 1)
+               return -EBUSY;
+
+       if (!cpu_online(cpu))
+               return -EINVAL;
+
+       cpu_hotplug_begin();
+
+       cpuhp_tasks_frozen = tasks_frozen;
+
+       err = notify_down_prepare(cpu);
+       if (err)
+               goto out_release;
+       err = takedown_cpu(cpu);
+       if (err)
+               goto out_release;
+
+       notify_dead(cpu);
 
 out_release:
        cpu_hotplug_done();