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[patch 18/20] cpu/hotplug: Let upcoming cpu bring itself fully up

From Thomas Gleixner <tglx@linutronix.de>
Newsgroups linux.kernel
Subject [patch 18/20] cpu/hotplug: Let upcoming cpu bring itself fully up
Date 2016-02-26 19:50 +0100
Message-ID <r6vCH-7sv-35@gated-at.bofh.it> (permalink)
References <r6vCG-7sv-3@gated-at.bofh.it>
Organization linux.* mail to news gateway

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Let the upcoming cpu kick the hotplug thread and let itself complete the
bringup. That way the controll side can just wait for the completion or later
when we made the hotplug machinery async not care at all.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 include/linux/cpuhotplug.h |    9 ++++--
 kernel/cpu.c               |   66 +++++++++++++++++++++++++--------------------
 kernel/sched/idle.c        |    2 +
 3 files changed, 45 insertions(+), 32 deletions(-)

Index: b/include/linux/cpuhotplug.h
===================================================================
--- a/include/linux/cpuhotplug.h
+++ b/include/linux/cpuhotplug.h
@@ -10,9 +10,6 @@ enum cpuhp_state {
 	CPUHP_AP_NOTIFY_STARTING,
 	CPUHP_AP_ONLINE,
 	CPUHP_TEARDOWN_CPU,
-	CPUHP_CPU_SET_ACTIVE,
-	CPUHP_KICK_AP_THREAD,
-	CPUHP_BP_ONLINE,
 	CPUHP_AP_ONLINE_IDLE,
 	CPUHP_AP_SMPBOOT_THREADS,
 	CPUHP_AP_NOTIFY_ONLINE,
@@ -86,4 +83,10 @@ static inline void cpuhp_remove_state_no
 	__cpuhp_remove_state(state, false);
 }
 
+#ifdef CONFIG_SMP
+void cpuhp_online_idle(enum cpuhp_state state);
+#else
+static inline void cpuhp_online_idle(enum cpuhp_state state) { }
+#endif
+
 #endif
Index: b/kernel/cpu.c
===================================================================
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -329,6 +329,14 @@ static int notify_starting(unsigned int
 	return 0;
 }
 
+static int bringup_wait_for_ap(unsigned int cpu)
+{
+	struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
+
+	wait_for_completion(&st->done);
+	return st->result;
+}
+
 static int bringup_cpu(unsigned int cpu)
 {
 	struct task_struct *idle = idle_thread_get(cpu);
@@ -340,8 +348,9 @@ static int bringup_cpu(unsigned int cpu)
 		cpu_notify(CPU_UP_CANCELED, cpu);
 		return ret;
 	}
+	ret = bringup_wait_for_ap(cpu);
 	BUG_ON(!cpu_online(cpu));
-	return 0;
+	return ret;
 }
 
 /*
@@ -470,7 +479,7 @@ static void cpuhp_thread_fun(unsigned in
 		}
 	} else {
 		/* Cannot happen .... */
-		BUG_ON(st->state < CPUHP_KICK_AP_THREAD);
+		BUG_ON(st->state < CPUHP_AP_ONLINE_IDLE);
 
 		/* Regular hotplug work */
 		if (st->state < st->target)
@@ -780,7 +789,7 @@ static int __ref _cpu_down(unsigned int
 	 * If the current CPU state is in the range of the AP hotplug thread,
 	 * then we need to kick the thread.
 	 */
-	if (st->state >= CPUHP_KICK_AP_THREAD) {
+	if (st->state > CPUHP_TEARDOWN_CPU) {
 		ret = cpuhp_kick_ap_work(cpu);
 		/*
 		 * The AP side has done the error rollback already. Just
@@ -793,11 +802,11 @@ static int __ref _cpu_down(unsigned int
 		 * We might have stopped still in the range of the AP hotplug
 		 * thread. Nothing to do anymore.
 		 */
-		if (st->state >= CPUHP_KICK_AP_THREAD)
+		if (st->state > CPUHP_TEARDOWN_CPU)
 			goto out;
 	}
 	/*
-	 * The AP brought itself down below CPUHP_KICK_AP_THREAD. So we need
+	 * The AP brought itself down to CPUHP_TEARDOWN_CPU. So we need
 	 * to do the further cleanups.
 	 */
 	ret = cpuhp_down_callbacks(cpu, st, cpuhp_bp_states, target);
@@ -859,18 +868,32 @@ void notify_cpu_starting(unsigned int cp
 
 /*
  * Called from the idle task. We need to set active here, so we can kick off
- * the stopper thread.
+ * the stopper thread and unpark the smpboot threads. If the target state is
+ * beyond CPUHP_AP_ONLINE_IDLE we kick cpuhp thread and let it bring up the
+ * cpu further.
  */
-static int cpuhp_set_cpu_active(unsigned int cpu)
+void cpuhp_online_idle(enum cpuhp_state state)
 {
-	struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
+	struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
+	unsigned int cpu = smp_processor_id();
+
+	/* Happens for the boot cpu */
+	if (state != CPUHP_AP_ONLINE_IDLE)
+		return;
+
+	st->state = CPUHP_AP_ONLINE_IDLE;
 
 	/* The cpu is marked online, set it active now */
 	set_cpu_active(cpu, true);
-	/* Unpark the stopper thread and the hotplug thread */
+	/* Unpark the stopper thread and the hotplug thread of this cpu */
 	stop_machine_unpark(cpu);
 	kthread_unpark(st->thread);
-	return 0;
+
+	/* Should we go further up ? */
+	if (st->target > CPUHP_AP_ONLINE_IDLE)
+		__cpuhp_kick_ap_work(st);
+	else
+		complete(&st->done);
 }
 
 /* Requires cpu_add_remove_lock to be held */
@@ -910,7 +933,7 @@ static int _cpu_up(unsigned int cpu, int
 	 * If the current CPU state is in the range of the AP hotplug thread,
 	 * then we need to kick the thread once more.
 	 */
-	if (st->state >= CPUHP_KICK_AP_THREAD) {
+	if (st->state > CPUHP_BRINGUP_CPU) {
 		ret = cpuhp_kick_ap_work(cpu);
 		/*
 		 * The AP side has done the error rollback already. Just
@@ -922,10 +945,10 @@ static int _cpu_up(unsigned int cpu, int
 
 	/*
 	 * Try to reach the target state. We max out on the BP at
-	 * CPUHP_KICK_AP_THREAD. After that the AP hotplug thread is
+	 * CPUHP_BRINGUP_CPU. After that the AP hotplug thread is
 	 * responsible for bringing it up to the target state.
 	 */
-	target = min((int)target, CPUHP_KICK_AP_THREAD);
+	target = min((int)target, CPUHP_BRINGUP_CPU);
 	ret = cpuhp_up_callbacks(cpu, st, cpuhp_bp_states, target);
 out:
 	cpu_hotplug_done();
@@ -1146,22 +1169,7 @@ static struct cpuhp_step cpuhp_bp_states
 		.teardown		= takedown_cpu,
 		.cant_stop		= true,
 	},
-	[CPUHP_CPU_SET_ACTIVE] = {
-		.name			= "cpu:active",
-		.startup		= cpuhp_set_cpu_active,
-		.teardown		= NULL,
-	},
-	[CPUHP_KICK_AP_THREAD] = {
-		.name			= "cpuhp:kickthread",
-		.startup		= cpuhp_kick_ap_work,
-		.teardown		= cpuhp_kick_ap_work,
-	},
 #endif
-	[CPUHP_BP_ONLINE] = {
-		.name			= "online",
-		.startup		= NULL,
-		.teardown		= NULL,
-	},
 };
 
 /* Application processor state steps */
@@ -1204,7 +1212,7 @@ static bool cpuhp_is_ap_state(enum cpuhp
 {
 	if (state >= CPUHP_AP_OFFLINE && state <= CPUHP_AP_ONLINE)
 		return true;
-	return state > CPUHP_BP_ONLINE;
+	return state > CPUHP_BRINGUP_CPU;
 }
 
 static struct cpuhp_step *cpuhp_get_step(enum cpuhp_state state)
Index: b/kernel/sched/idle.c
===================================================================
--- a/kernel/sched/idle.c
+++ b/kernel/sched/idle.c
@@ -4,6 +4,7 @@
 #include <linux/sched.h>
 #include <linux/cpu.h>
 #include <linux/cpuidle.h>
+#include <linux/cpuhotplug.h>
 #include <linux/tick.h>
 #include <linux/mm.h>
 #include <linux/stackprotector.h>
@@ -276,5 +277,6 @@ static void cpu_idle_loop(void)
 void cpu_startup_entry(enum cpuhp_state state)
 {
 	arch_cpu_idle_prepare();
+	cpuhp_online_idle(state);
 	cpu_idle_loop();
 }

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Thread

[patch 00/20] cpu/hotplug: Core infrastructure for cpu hotplug rework Thomas Gleixner <tglx@linutronix.de> - 2016-02-26 19:50 +0100
  [patch 14/20] cpu/hotplug: Split out the state walk into functions Thomas Gleixner <tglx@linutronix.de> - 2016-02-26 19:50 +0100
    [tip:smp/hotplug] cpu/hotplug: Split out the state walk into  functions tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2016-03-01 21:00 +0100
  [patch 17/20] arch/hotplug: Call into idle with a proper state Thomas Gleixner <tglx@linutronix.de> - 2016-02-26 19:50 +0100
    [tip:smp/hotplug] arch/hotplug: Call into idle with a proper state tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2016-03-01 21:00 +0100
  [patch 04/20] cpu/hotplug: Split out cpu down functions Thomas Gleixner <tglx@linutronix.de> - 2016-02-26 19:50 +0100
    [tip:smp/hotplug] cpu/hotplug: Split out cpu down functions tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2016-03-01 21:00 +0100
      Re: [tip:smp/hotplug] cpu/hotplug: Split out cpu down functions "Srivatsa S. Bhat" <srivatsa@csail.mit.edu> - 2016-03-03 00:10 +0100
  [patch 03/20] cpu/hotplug: Restructure cpu_up code Thomas Gleixner <tglx@linutronix.de> - 2016-02-26 19:50 +0100
    [tip:smp/hotplug] cpu/hotplug: Restructure cpu_up code tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2016-03-01 21:00 +0100
      Re: [tip:smp/hotplug] cpu/hotplug: Restructure cpu_up code "Srivatsa S. Bhat" <srivatsa@csail.mit.edu> - 2016-03-03 00:00 +0100
  [patch 16/20] cpu/hotplug: Move online calls to hotplugged cpu Thomas Gleixner <tglx@linutronix.de> - 2016-02-26 19:50 +0100
    [tip:smp/hotplug] cpu/hotplug: Move online calls to hotplugged cpu tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2016-03-01 21:00 +0100
  [patch 02/20] cpu/hotplug: Restructure FROZEN state handling Thomas Gleixner <tglx@linutronix.de> - 2016-02-26 19:50 +0100
    [tip:smp/hotplug] cpu/hotplug: Restructure FROZEN state handling tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2016-03-01 21:00 +0100
      Re: [tip:smp/hotplug] cpu/hotplug: Restructure FROZEN state handling "Srivatsa S. Bhat" <srivatsa@csail.mit.edu> - 2016-03-03 00:10 +0100
      Re: [tip:smp/hotplug] cpu/hotplug: Restructure FROZEN state handling "Srivatsa S. Bhat" <srivatsa@csail.mit.edu> - 2016-03-03 00:50 +0100
  [patch 11/20] cpu/hotplug: Implement setup/removal interface Thomas Gleixner <tglx@linutronix.de> - 2016-02-26 19:50 +0100
    [tip:smp/hotplug] cpu/hotplug: Implement setup/removal interface tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2016-03-01 21:00 +0100
  [patch 12/20] cpu/hotplug: Move scheduler cpu_online notifier to  hotplug core Thomas Gleixner <tglx@linutronix.de> - 2016-02-26 19:50 +0100
    [tip:smp/hotplug] cpu/hotplug: Move scheduler cpu_online notifier  to hotplug core tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2016-03-01 21:00 +0100
  [patch 18/20] cpu/hotplug: Let upcoming cpu bring itself fully up Thomas Gleixner <tglx@linutronix.de> - 2016-02-26 19:50 +0100
    [tip:smp/hotplug] cpu/hotplug: Let upcoming cpu bring itself fully  up tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2016-03-01 21:00 +0100
    Re: [patch 18/20] cpu/hotplug: Let upcoming cpu bring itself fully up Richard Cochran <richardcochran@gmail.com> - 2016-03-02 18:30 +0100
  [patch 15/20] cpu/hotplug: Create hotplug threads Thomas Gleixner <tglx@linutronix.de> - 2016-02-26 19:50 +0100
    [tip:smp/hotplug] cpu/hotplug: Create hotplug threads tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2016-03-01 21:00 +0100
  [patch 09/20] cpu/hotplug: Add sysfs state interface Thomas Gleixner <tglx@linutronix.de> - 2016-02-26 19:50 +0100
    [tip:smp/hotplug] cpu/hotplug: Add sysfs state interface tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2016-03-01 21:00 +0100
      Re: [tip:smp/hotplug] cpu/hotplug: Add sysfs state interface Peter Zijlstra <peterz@infradead.org> - 2016-03-02 13:50 +0100
  [patch 06/20] cpu/hotplug: Convert to a state machine for the control  processor Thomas Gleixner <tglx@linutronix.de> - 2016-02-26 19:50 +0100
    [tip:smp/hotplug] cpu/hotplug: Convert to a state machine for the  control processor tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2016-03-01 21:00 +0100
      Re: [tip:smp/hotplug] cpu/hotplug: Convert to a state machine for  the control processor Peter Zijlstra <peterz@infradead.org> - 2016-03-02 12:30 +0100
  [patch 20/20] rcu: Make CPU_DYING_IDLE an explicit call Thomas Gleixner <tglx@linutronix.de> - 2016-02-26 19:50 +0100
    Re: [patch 20/20] rcu: Make CPU_DYING_IDLE an explicit call "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-02-27 03:20 +0100
      Re: [patch 20/20] rcu: Make CPU_DYING_IDLE an explicit call "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-02-27 03:30 +0100
        Re: [patch 20/20] rcu: Make CPU_DYING_IDLE an explicit call Thomas Gleixner <tglx@linutronix.de> - 2016-02-27 08:50 +0100
          Re: [patch 20/20] rcu: Make CPU_DYING_IDLE an explicit call "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-02-27 12:10 +0100
            Re: [patch 20/20] rcu: Make CPU_DYING_IDLE an explicit call Thomas Gleixner <tglx@linutronix.de> - 2016-02-27 12:40 +0100
              Re: [patch 20/20] rcu: Make CPU_DYING_IDLE an explicit call "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-02-27 17:40 +0100
    [tip:smp/hotplug] rcu: Make CPU_DYING_IDLE an explicit call tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2016-03-01 21:00 +0100
      Re: [tip:smp/hotplug] rcu: Make CPU_DYING_IDLE an explicit call "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-03-02 21:20 +0100
        Re: [tip:smp/hotplug] rcu: Make CPU_DYING_IDLE an explicit call Thomas Gleixner <tglx@linutronix.de> - 2016-03-03 08:40 +0100
        [tip:smp/hotplug] cpu/hotplug: Plug death reporting race tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2016-03-03 11:10 +0100
          Re: [tip:smp/hotplug] cpu/hotplug: Plug death reporting race "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-03-03 15:20 +0100
  [patch 08/20] cpu/hotplug: Hand in target state to _cpu_up/down Thomas Gleixner <tglx@linutronix.de> - 2016-02-26 19:50 +0100
    [tip:smp/hotplug] cpu/hotplug: Hand in target state to _cpu_up/down tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2016-03-01 21:00 +0100
  [patch 19/20] cpu/hotplug: Make wait for dead cpu completion based Thomas Gleixner <tglx@linutronix.de> - 2016-02-26 19:50 +0100
    [tip:smp/hotplug] cpu/hotplug: Make wait for dead cpu completion  based tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2016-03-01 21:00 +0100
  [patch 07/20] cpu/hotplug: Convert the hotplugged cpu work to a state  machine Thomas Gleixner <tglx@linutronix.de> - 2016-02-26 20:00 +0100
    [tip:smp/hotplug] cpu/hotplug: Convert the hotplugged cpu work to a  state machine tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2016-03-01 21:00 +0100
  [patch 01/20] idle: Move x86ism out of generic code Thomas Gleixner <tglx@linutronix.de> - 2016-02-26 20:00 +0100
    Re: [patch 01/20] idle: Move x86ism out of generic code Brian Gerst <brgerst@gmail.com> - 2016-02-27 21:30 +0100
      Re: [patch 01/20] idle: Move x86ism out of generic code Thomas Gleixner <tglx@linutronix.de> - 2016-02-29 20:40 +0100
        Re: [patch 01/20] idle: Move x86ism out of generic code Will Deacon <will.deacon@arm.com> - 2016-02-29 20:50 +0100
          Re: [patch 01/20] idle: Move x86ism out of generic code Thomas Gleixner <tglx@linutronix.de> - 2016-02-29 21:10 +0100

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