cpu/hotplug: Restructure cpu_up code

Split out into separate functions, so we can convert it to a state machine.

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/20160226182340.429389195@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 47 insertions, 22 deletions

diff --git a/kernel/cpu.c b/kernel/cpu.c
index 41a6cb85c0af..15a413639abc 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -228,6 +228,43 @@ static int cpu_notify(unsigned long val, unsigned int cpu)
         return __cpu_notify(val, cpu, -1, NULL);
 }
 
+/* Notifier wrappers for transitioning to state machine */
+static int notify_prepare(unsigned int cpu)
+{
+        int nr_calls = 0;
+        int ret;
+
+        ret = __cpu_notify(CPU_UP_PREPARE, cpu, -1, &nr_calls);
+        if (ret) {
+                nr_calls--;
+                printk(KERN_WARNING "%s: attempt to bring up CPU %u failed\n",
+                                __func__, cpu);
+                __cpu_notify(CPU_UP_CANCELED, cpu, nr_calls, NULL);
+        }
+        return ret;
+}
+
+static int notify_online(unsigned int cpu)
+{
+        cpu_notify(CPU_ONLINE, cpu);
+        return 0;
+}
+
+static int bringup_cpu(unsigned int cpu)
+{
+        struct task_struct *idle = idle_thread_get(cpu);
+        int ret;
+
+        /* Arch-specific enabling code. */
+        ret = __cpu_up(cpu, idle);
+        if (ret) {
+                cpu_notify(CPU_UP_CANCELED, cpu);
+                return ret;
+        }
+        BUG_ON(!cpu_online(cpu));
+        return 0;
+}
+
 #ifdef CONFIG_HOTPLUG_CPU
 
 static void cpu_notify_nofail(unsigned long val, unsigned int cpu)
@@ -481,7 +518,7 @@ void smpboot_thread_init(void)
 static int _cpu_up(unsigned int cpu, int tasks_frozen)
 {
         struct task_struct *idle;
-        int ret, nr_calls = 0;
+        int ret;
 
         cpu_hotplug_begin();
 
@@ -496,33 +533,21 @@ static int _cpu_up(unsigned int cpu, int tasks_frozen)
                 goto out;
         }
 
+        cpuhp_tasks_frozen = tasks_frozen;
+
         ret = smpboot_create_threads(cpu);
         if (ret)
                 goto out;
 
-        cpuhp_tasks_frozen = tasks_frozen;
-
-        ret = __cpu_notify(CPU_UP_PREPARE, cpu, -1, &nr_calls);
-        if (ret) {
-                nr_calls--;
-                pr_warn("%s: attempt to bring up CPU %u failed\n",
-                        __func__, cpu);
-                goto out_notify;
-        }
-
-        /* Arch-specific enabling code. */
-        ret = __cpu_up(cpu, idle);
-
-        if (ret != 0)
-                goto out_notify;
-        BUG_ON(!cpu_online(cpu));
+        ret = notify_prepare(cpu);
+        if (ret)
+                goto out;
 
-        /* Now call notifier in preparation. */
-        cpu_notify(CPU_ONLINE, cpu);
+        ret = bringup_cpu(cpu);
+        if (ret)
+                goto out;
 
-out_notify:
-        if (ret != 0)
-                __cpu_notify(CPU_UP_CANCELED, cpu, nr_calls, NULL);
+        notify_online(cpu);
 out:
         cpu_hotplug_done();