linux-kernel - [PATCH 09/22] mm/vmstat: Convert to hotplug state machine

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Date:   Sun, 27 Nov 2016 00:13:37 +0100
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     linux-kernel@...r.kernel.org
Cc:     rt@...utronix.de, tglx@...utronix.de,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Johannes Weiner <hannes@...xchg.org>, linux-mm@...ck.org
Subject: [PATCH 09/22] mm/vmstat: Convert to hotplug state machine

Install the callbacks via the state machine, but do not invoke them as we
can initialize the node state without calling the callbacks on all online
CPUs.

start_shepherd_timer() is now called outside the get_online_cpus() block
which is safe as it only operates on cpu possible mask.

Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Vlastimil Babka <vbabka@...e.cz>
Cc: Mel Gorman <mgorman@...hsingularity.net>
Cc: Johannes Weiner <hannes@...xchg.org>
Cc: linux-mm@...ck.org
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
---
 include/linux/cpuhotplug.h |  1 +
 mm/vmstat.c                | 76 +++++++++++++++++++++-------------------------
 2 files changed, 36 insertions(+), 41 deletions(-)

diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
index 18bcfeb2463e..4ebd1bc27f8d 100644
--- a/include/linux/cpuhotplug.h
+++ b/include/linux/cpuhotplug.h
@@ -20,6 +20,7 @@ enum cpuhp_state {
 	CPUHP_VIRT_NET_DEAD,
 	CPUHP_SLUB_DEAD,
 	CPUHP_MM_WRITEBACK_DEAD,
+	CPUHP_MM_VMSTAT_DEAD,
 	CPUHP_SOFTIRQ_DEAD,
 	CPUHP_NET_MVNETA_DEAD,
 	CPUHP_CPUIDLE_DEAD,
diff --git a/mm/vmstat.c b/mm/vmstat.c
index b96dcec7e7d7..dfe3cb9f2c36 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -1726,64 +1726,58 @@ static void __init init_cpu_node_state(void)
 		node_set_state(node, N_CPU);
 }
 
-static void vmstat_cpu_dead(int node)
+static int vmstat_cpu_online(unsigned int cpu)
+{
+	refresh_zone_stat_thresholds();
+	node_set_state(cpu_to_node(cpu), N_CPU);
+	return 0;
+}
+
+static int vmstat_cpu_down_prep(unsigned int cpu)
+{
+	cancel_delayed_work_sync(&per_cpu(vmstat_work, cpu));
+	return 0;
+}
+
+static int vmstat_cpu_dead(unsigned int cpu)
 {
 	const struct cpumask *node_cpus;
+	int node;
 
+	node = cpu_to_node(cpu);
+
+	refresh_zone_stat_thresholds();
 	node_cpus = cpumask_of_node(node);
 	if (cpumask_weight(node_cpus) > 0)
-		return;
+		return 0;
 
 	node_clear_state(node, N_CPU);
+	return 0;
 }
 
-/*
- * Use the cpu notifier to insure that the thresholds are recalculated
- * when necessary.
- */
-static int vmstat_cpuup_callback(struct notifier_block *nfb,
-		unsigned long action,
-		void *hcpu)
-{
-	long cpu = (long)hcpu;
-
-	switch (action) {
-	case CPU_ONLINE:
-	case CPU_ONLINE_FROZEN:
-		refresh_zone_stat_thresholds();
-		node_set_state(cpu_to_node(cpu), N_CPU);
-		break;
-	case CPU_DOWN_PREPARE:
-	case CPU_DOWN_PREPARE_FROZEN:
-		cancel_delayed_work_sync(&per_cpu(vmstat_work, cpu));
-		break;
-	case CPU_DOWN_FAILED:
-	case CPU_DOWN_FAILED_FROZEN:
-		break;
-	case CPU_DEAD:
-	case CPU_DEAD_FROZEN:
-		refresh_zone_stat_thresholds();
-		vmstat_cpu_dead(cpu_to_node(cpu));
-		break;
-	default:
-		break;
-	}
-	return NOTIFY_OK;
-}
-
-static struct notifier_block vmstat_notifier =
-	{ &vmstat_cpuup_callback, NULL, 0 };
 #endif
 
 static int __init setup_vmstat(void)
 {
 #ifdef CONFIG_SMP
-	cpu_notifier_register_begin();
-	__register_cpu_notifier(&vmstat_notifier);
+	int ret;
+
+	ret = cpuhp_setup_state_nocalls(CPUHP_MM_VMSTAT_DEAD, "mm/vmstat:dead",
+					NULL, vmstat_cpu_dead);
+	if (ret < 0)
+		pr_err("vmstat: failed to register 'dead' hotplug state\n");
+
+	ret = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN, "mm/vmstat:online",
+					vmstat_cpu_online,
+					vmstat_cpu_down_prep);
+	if (ret < 0)
+		pr_err("vmstat: failed to register 'online' hotplug state\n");
+
+	get_online_cpus();
 	init_cpu_node_state();
+	put_online_cpus();
 
 	start_shepherd_timer();
-	cpu_notifier_register_done();
 #endif
 #ifdef CONFIG_PROC_FS
 	proc_create("buddyinfo", S_IRUGO, NULL, &fragmentation_file_operations);
-- 
2.10.2