linux-kernel - [tip:smp/hotplug] cpu/hotplug: Restructure cpu

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Date:	Tue, 1 Mar 2016 11:52:11 -0800
From:	tip-bot for Thomas Gleixner <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	hpa@...or.com, rusty@...tcorp.com.au, mingo@...nel.org,
	akpm@...ux-foundation.org, peterz@...radead.org, srivatsa@....edu,
	torvalds@...ux-foundation.org, oleg@...hat.com,
	paulmck@...ux.vnet.ibm.com, tglx@...utronix.de,
	linux-kernel@...r.kernel.org, tj@...nel.org, pjt@...gle.com,
	rafael.j.wysocki@...el.com, bigeasy@...utronix.de,
	arjan@...ux.intel.com, rostedt@...dmis.org, riel@...hat.com
Subject: [tip:smp/hotplug] cpu/hotplug: Restructure cpu_up code

Commit-ID:  ba997462435f48ad1501320e9da8770fd40c59b1
Gitweb:     http://git.kernel.org/tip/ba997462435f48ad1501320e9da8770fd40c59b1
Author:     Thomas Gleixner <tglx@...utronix.de>
AuthorDate: Fri, 26 Feb 2016 18:43:24 +0000
Committer:  Thomas Gleixner <tglx@...utronix.de>
CommitDate: Tue, 1 Mar 2016 20:36:53 +0100

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@...utronix.de>
Cc: linux-arch@...r.kernel.org
Cc: Rik van Riel <riel@...hat.com>
Cc: Rafael Wysocki <rafael.j.wysocki@...el.com>
Cc: "Srivatsa S. Bhat" <srivatsa@....edu>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Arjan van de Ven <arjan@...ux.intel.com>
Cc: Sebastian Siewior <bigeasy@...utronix.de>
Cc: Rusty Russell <rusty@...tcorp.com.au>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Oleg Nesterov <oleg@...hat.com>
Cc: Tejun Heo <tj@...nel.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Paul McKenney <paulmck@...ux.vnet.ibm.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Paul Turner <pjt@...gle.com>
Link: http://lkml.kernel.org/r/20160226182340.429389195@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
---
 kernel/cpu.c | 69 +++++++++++++++++++++++++++++++++++++++++-------------------
 1 file changed, 47 insertions(+), 22 deletions(-)

diff --git a/kernel/cpu.c b/kernel/cpu.c
index 41a6cb8..15a4136 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();