[tip:smp/hotplug] sched/hotplug: Move migration CPU_DYING to sched_cpu_dying()

tip-bot for Thomas Gleixner
2016-05-06T13:08:12Z

Commit-ID: f2785ddb5367e217365099294b89d6a84668069e
Gitweb: http://git.kernel.org/tip/f2785ddb5367e217365099294b89d6a84668069e
Author: Thomas Gleixner <tglx@linutronix.de>
AuthorDate: Thu, 10 Mar 2016 12:54:18 +0100
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitDate: Fri, 6 May 2016 14:58:25 +0200

sched/hotplug: Move migration CPU_DYING to sched_cpu_dying()

Remove the hotplug notifier and make it an explicit state.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/20160310120025.502222097@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
include/linux/cpu.h | 2 --
include/linux/sched.h | 6 +++++
kernel/cpu.c | 2 +-
kernel/sched/core.c | 72 ++++++++++++++++-----------------------------------
4 files changed, 29 insertions(+), 53 deletions(-)

diff --git a/include/linux/cpu.h b/include/linux/cpu.h
index b22b000..21597dc 100644
--- a/include/linux/cpu.h
+++ b/include/linux/cpu.h
@@ -59,9 +59,7 @@ struct notifier_block;
* CPU notifier priorities.
*/
enum {
- /* migration should happen before other stuff but after perf */
CPU_PRI_PERF = 20,
- CPU_PRI_MIGRATION = 10,

/* bring up workqueues before normal notifiers and down after */
CPU_PRI_WORKQUEUE_UP = 5,
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 1e5f961..47835cf 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -376,6 +376,12 @@ extern int sched_cpu_starting(unsigned int cpu);
extern int sched_cpu_activate(unsigned int cpu);
extern int sched_cpu_deactivate(unsigned int cpu);

+#ifdef CONFIG_HOTPLUG_CPU
+extern int sched_cpu_dying(unsigned int cpu);
+#else
+# define sched_cpu_dying NULL
+#endif
+
extern void sched_show_task(struct task_struct *p);

#ifdef CONFIG_LOCKUP_DETECTOR
diff --git a/kernel/cpu.c b/kernel/cpu.c
index c134a35..d6eeb8c 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -1223,7 +1223,7 @@ static struct cpuhp_step cpuhp_ap_states[] = {
[CPUHP_AP_SCHED_STARTING] = {
.name = "sched:starting",
.startup = sched_cpu_starting,
- .teardown = NULL,
+ .teardown = sched_cpu_dying,
},
/*
* Low level startup/teardown notifiers. Run with interrupts
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 8d8d903..a9a65ed 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -5411,51 +5411,6 @@ static void set_rq_offline(struct rq *rq)
}
}

-/*
- * migration_call - callback that gets triggered when a CPU is added.
- * Here we can start up the necessary migration thread for the new CPU.
- */
-static int
-migration_call(struct notifier_block *nfb, unsigned long action, void *hcpu)
-{
- int cpu = (long)hcpu;
- unsigned long flags;
- struct rq *rq = cpu_rq(cpu);
-
- switch (action & ~CPU_TASKS_FROZEN) {
-
-#ifdef CONFIG_HOTPLUG_CPU
- case CPU_DYING:
- sched_ttwu_pending();
- /* Update our root-domain */
- raw_spin_lock_irqsave(&rq->lock, flags);
- if (rq->rd) {
- BUG_ON(!cpumask_test_cpu(cpu, rq->rd->span));
- set_rq_offline(rq);
- }
- migrate_tasks(rq);
- BUG_ON(rq->nr_running != 1); /* the migration thread */
- raw_spin_unlock_irqrestore(&rq->lock, flags);
- calc_load_migrate(rq);
- break;
-#endif
- }
-
- update_max_interval();
-
- return NOTIFY_OK;
-}
-
-/*
- * Register at high priority so that task migration (migrate_all_tasks)
- * happens before everything else. This has to be lower priority than
- * the notifier in the perf_event subsystem, though.
- */
-static struct notifier_block migration_notifier = {
- .notifier_call = migration_call,
- .priority = CPU_PRI_MIGRATION,
-};
-
static void set_cpu_rq_start_time(unsigned int cpu)
{
struct rq *rq = cpu_rq(cpu);
@@ -7158,6 +7113,28 @@ int sched_cpu_starting(unsigned int cpu)
return 0;
}

+#ifdef CONFIG_HOTPLUG_CPU
+int sched_cpu_dying(unsigned int cpu)
+{
+ struct rq *rq = cpu_rq(cpu);
+ unsigned long flags;
+
+ /* Handle pending wakeups and then migrate everything off */
+ sched_ttwu_pending();
+ raw_spin_lock_irqsave(&rq->lock, flags);
+ if (rq->rd) {
+ BUG_ON(!cpumask_test_cpu(cpu, rq->rd->span));
+ set_rq_offline(rq);
+ }
+ migrate_tasks(rq);
+ BUG_ON(rq->nr_running != 1);
+ raw_spin_unlock_irqrestore(&rq->lock, flags);
+ calc_load_migrate(rq);
+ update_max_interval();
+ return 0;
+}
+#endif
+
void __init sched_init_smp(void)
{
cpumask_var_t non_isolated_cpus;
@@ -7194,12 +7171,7 @@ void __init sched_init_smp(void)

static int __init migration_init(void)
{
- void *cpu = (void *)(long)smp_processor_id();
-
sched_rq_cpu_starting(smp_processor_id());
- migration_call(&migration_notifier, CPU_ONLINE, cpu);
- register_cpu_notifier(&migration_notifier);
-
return 0;
}
early_initcall(migration_init);