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Subject[tip:smp/hotplug] sched/nohz: Convert to hotplug state machine
Commit-ID:  703c96e4971c3d2383d9bf248fa656f154250edc
Gitweb: http://git.kernel.org/tip/703c96e4971c3d2383d9bf248fa656f154250edc
Author: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
AuthorDate: Thu, 17 Nov 2016 19:35:34 +0100
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitDate: Mon, 21 Nov 2016 16:37:07 +0100

sched/nohz: Convert to hotplug state machine

Install the callbacks via the state machine.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: rt@linuxtronix.de
Link: http://lkml.kernel.org/r/20161117183541.8588-14-bigeasy@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

---
kernel/time/tick-sched.c | 33 ++++++++++++++-------------------
1 file changed, 14 insertions(+), 19 deletions(-)

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 3bcb61b..71496a2 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -390,24 +390,16 @@ static int __init tick_nohz_full_setup(char *str)
}
__setup("nohz_full=", tick_nohz_full_setup);

-static int tick_nohz_cpu_down_callback(struct notifier_block *nfb,
- unsigned long action,
- void *hcpu)
+static int tick_nohz_cpu_down(unsigned int cpu)
{
- unsigned int cpu = (unsigned long)hcpu;
-
- switch (action & ~CPU_TASKS_FROZEN) {
- case CPU_DOWN_PREPARE:
- /*
- * The boot CPU handles housekeeping duty (unbound timers,
- * workqueues, timekeeping, ...) on behalf of full dynticks
- * CPUs. It must remain online when nohz full is enabled.
- */
- if (tick_nohz_full_running && tick_do_timer_cpu == cpu)
- return NOTIFY_BAD;
- break;
- }
- return NOTIFY_OK;
+ /*
+ * The boot CPU handles housekeeping duty (unbound timers,
+ * workqueues, timekeeping, ...) on behalf of full dynticks
+ * CPUs. It must remain online when nohz full is enabled.
+ */
+ if (tick_nohz_full_running && tick_do_timer_cpu == cpu)
+ return -EBUSY;
+ return 0;
}

static int tick_nohz_init_all(void)
@@ -428,7 +420,7 @@ static int tick_nohz_init_all(void)

void __init tick_nohz_init(void)
{
- int cpu;
+ int cpu, ret;

if (!tick_nohz_full_running) {
if (tick_nohz_init_all() < 0)
@@ -469,7 +461,10 @@ void __init tick_nohz_init(void)
for_each_cpu(cpu, tick_nohz_full_mask)
context_tracking_cpu_set(cpu);

- cpu_notifier(tick_nohz_cpu_down_callback, 0);
+ ret = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN,
+ "kernel/nohz:predown", NULL,
+ tick_nohz_cpu_down);
+ WARN_ON(ret < 0);
pr_info("NO_HZ: Full dynticks CPUs: %*pbl.\n",
cpumask_pr_args(tick_nohz_full_mask));

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