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Date: Tue, 1 Mar 2016 11:57:00 -0800
From: tip-bot for Thomas Gleixner <tipbot@...or.com>
To: linux-tip-commits@...r.kernel.org
Cc: tglx@...utronix.de, riel@...hat.com, rostedt@...dmis.org,
rafael.j.wysocki@...el.com, bigeasy@...utronix.de, hpa@...or.com,
mingo@...nel.org, peterz@...radead.org, tj@...nel.org,
arjan@...ux.intel.com, rusty@...tcorp.com.au, oleg@...hat.com,
linux-kernel@...r.kernel.org, pjt@...gle.com, srivatsa@....edu,
torvalds@...ux-foundation.org, paulmck@...ux.vnet.ibm.com,
akpm@...ux-foundation.org
Subject: [tip:smp/hotplug] cpu/hotplug: Create hotplug threads
Commit-ID: 4cb28ced23c4f222ff4e3f39898017e52161a9c9
Gitweb: http://git.kernel.org/tip/4cb28ced23c4f222ff4e3f39898017e52161a9c9
Author: Thomas Gleixner <tglx@...utronix.de>
AuthorDate: Fri, 26 Feb 2016 18:43:38 +0000
Committer: Thomas Gleixner <tglx@...utronix.de>
CommitDate: Tue, 1 Mar 2016 20:36:56 +0100
cpu/hotplug: Create hotplug threads
In order to let the hotplugged cpu take care of the setup/teardown, we need a
seperate hotplug thread.
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/20160226182341.454541272@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
---
kernel/cpu.c | 145 ++++++++++++++++++++++++++++++++++++++++++++++++++++++-
kernel/smp.c | 1 +
kernel/smpboot.h | 2 +
3 files changed, 147 insertions(+), 1 deletion(-)
diff --git a/kernel/cpu.c b/kernel/cpu.c
index 9572ca0..9048c33 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -22,6 +22,7 @@
#include <linux/lockdep.h>
#include <linux/tick.h>
#include <linux/irq.h>
+#include <linux/smpboot.h>
#include <trace/events/power.h>
#define CREATE_TRACE_POINTS
@@ -33,10 +34,24 @@
* cpuhp_cpu_state - Per cpu hotplug state storage
* @state: The current cpu state
* @target: The target state
+ * @thread: Pointer to the hotplug thread
+ * @should_run: Thread should execute
+ * @cb_stat: The state for a single callback (install/uninstall)
+ * @cb: Single callback function (install/uninstall)
+ * @result: Result of the operation
+ * @done: Signal completion to the issuer of the task
*/
struct cpuhp_cpu_state {
enum cpuhp_state state;
enum cpuhp_state target;
+#ifdef CONFIG_SMP
+ struct task_struct *thread;
+ bool should_run;
+ enum cpuhp_state cb_state;
+ int (*cb)(unsigned int cpu);
+ int result;
+ struct completion done;
+#endif
};
static DEFINE_PER_CPU(struct cpuhp_cpu_state, cpuhp_state);
@@ -394,6 +409,134 @@ static int cpuhp_up_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st,
return ret;
}
+/*
+ * The cpu hotplug threads manage the bringup and teardown of the cpus
+ */
+static void cpuhp_create(unsigned int cpu)
+{
+ struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
+
+ init_completion(&st->done);
+}
+
+static int cpuhp_should_run(unsigned int cpu)
+{
+ struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
+
+ return st->should_run;
+}
+
+/* Execute the teardown callbacks. Used to be CPU_DOWN_PREPARE */
+static int cpuhp_ap_offline(unsigned int cpu, struct cpuhp_cpu_state *st)
+{
+ enum cpuhp_state target = max((int)st->target, CPUHP_AP_ONLINE);
+
+ return cpuhp_down_callbacks(cpu, st, cpuhp_ap_states, target);
+}
+
+/* Execute the online startup callbacks. Used to be CPU_ONLINE */
+static int cpuhp_ap_online(unsigned int cpu, struct cpuhp_cpu_state *st)
+{
+ return cpuhp_up_callbacks(cpu, st, cpuhp_ap_states, st->target);
+}
+
+/*
+ * Execute teardown/startup callbacks on the plugged cpu. Also used to invoke
+ * callbacks when a state gets [un]installed at runtime.
+ */
+static void cpuhp_thread_fun(unsigned int cpu)
+{
+ struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
+ int ret = 0;
+
+ /*
+ * Paired with the mb() in cpuhp_kick_ap_work and
+ * cpuhp_invoke_ap_callback, so the work set is consistent visible.
+ */
+ smp_mb();
+ if (!st->should_run)
+ return;
+
+ st->should_run = false;
+
+ /* Single callback invocation for [un]install ? */
+ if (st->cb) {
+ if (st->cb_state < CPUHP_AP_ONLINE) {
+ local_irq_disable();
+ ret = cpuhp_invoke_callback(cpu, st->cb_state, st->cb);
+ local_irq_enable();
+ } else {
+ ret = cpuhp_invoke_callback(cpu, st->cb_state, st->cb);
+ }
+ } else {
+ /* Regular hotplug work */
+ if (st->state < st->target)
+ ret = cpuhp_ap_online(cpu, st);
+ else if (st->state > st->target)
+ ret = cpuhp_ap_offline(cpu, st);
+ }
+ st->result = ret;
+ complete(&st->done);
+}
+
+/* Invoke a single callback on a remote cpu */
+static int cpuhp_invoke_ap_callback(int cpu, enum cpuhp_state state,
+ int (*cb)(unsigned int))
+{
+ struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
+
+ if (!cpu_online(cpu))
+ return 0;
+
+ st->cb_state = state;
+ st->cb = cb;
+ /*
+ * Make sure the above stores are visible before should_run becomes
+ * true. Paired with the mb() above in cpuhp_thread_fun()
+ */
+ smp_mb();
+ st->should_run = true;
+ wake_up_process(st->thread);
+ wait_for_completion(&st->done);
+ return st->result;
+}
+
+/* Regular hotplug invocation of the AP hotplug thread */
+static int cpuhp_kick_ap_work(unsigned int cpu)
+{
+ struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
+ enum cpuhp_state state = st->state;
+
+ trace_cpuhp_enter(cpu, st->target, state, cpuhp_kick_ap_work);
+ st->result = 0;
+ st->cb = NULL;
+ /*
+ * Make sure the above stores are visible before should_run becomes
+ * true. Paired with the mb() above in cpuhp_thread_fun()
+ */
+ smp_mb();
+ st->should_run = true;
+ wake_up_process(st->thread);
+ wait_for_completion(&st->done);
+ trace_cpuhp_exit(cpu, st->state, state, st->result);
+ return st->result;
+}
+
+static struct smp_hotplug_thread cpuhp_threads = {
+ .store = &cpuhp_state.thread,
+ .create = &cpuhp_create,
+ .thread_should_run = cpuhp_should_run,
+ .thread_fn = cpuhp_thread_fun,
+ .thread_comm = "cpuhp/%u",
+ .selfparking = true,
+};
+
+void __init cpuhp_threads_init(void)
+{
+ BUG_ON(smpboot_register_percpu_thread(&cpuhp_threads));
+ kthread_unpark(this_cpu_read(cpuhp_state.thread));
+}
+
#ifdef CONFIG_HOTPLUG_CPU
EXPORT_SYMBOL(register_cpu_notifier);
EXPORT_SYMBOL(__register_cpu_notifier);
@@ -997,7 +1140,7 @@ static int cpuhp_cb_check(enum cpuhp_state state)
static bool cpuhp_is_ap_state(enum cpuhp_state state)
{
- return (state > CPUHP_AP_OFFLINE && state < CPUHP_AP_ONLINE);
+ return (state >= CPUHP_AP_OFFLINE && state <= CPUHP_AP_ONLINE);
}
static struct cpuhp_step *cpuhp_get_step(enum cpuhp_state state)
diff --git a/kernel/smp.c b/kernel/smp.c
index d903c02..822ffb1 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -569,6 +569,7 @@ void __init smp_init(void)
unsigned int cpu;
idle_threads_init();
+ cpuhp_threads_init();
/* FIXME: This should be done in userspace --RR */
for_each_present_cpu(cpu) {
diff --git a/kernel/smpboot.h b/kernel/smpboot.h
index 6b5f020..485b81c 100644
--- a/kernel/smpboot.h
+++ b/kernel/smpboot.h
@@ -17,4 +17,6 @@ int smpboot_create_threads(unsigned int cpu);
int smpboot_park_threads(unsigned int cpu);
int smpboot_unpark_threads(unsigned int cpu);
+void __init cpuhp_threads_init(void);
+
#endif
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