oprofile/nmi timer: Convert to hotplug state machine

Install the callbacks via the state machine and let the core invoke
the callbacks on the already online CPUs.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: oprofile-list@lists.sf.net
Cc: Robert Richter <rric@kernel.org>
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/20161126231350.10321-6-bigeasy@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 19 insertions, 39 deletions

diff --git a/drivers/oprofile/nmi_timer_int.c b/drivers/oprofile/nmi_timer_int.c
index 9559829fb234..e65a576e4032 100644
--- a/drivers/oprofile/nmi_timer_int.c
+++ b/drivers/oprofile/nmi_timer_int.c
@@ -59,25 +59,16 @@ static void nmi_timer_stop_cpu(int cpu)
                 perf_event_disable(event);
 }
 
-static int nmi_timer_cpu_notifier(struct notifier_block *b, unsigned long action,
-                                  void *data)
+static int nmi_timer_cpu_online(unsigned int cpu)
 {
-        int cpu = (unsigned long)data;
-        switch (action) {
-        case CPU_DOWN_FAILED:
-        case CPU_ONLINE:
-                nmi_timer_start_cpu(cpu);
-                break;
-        case CPU_DOWN_PREPARE:
-                nmi_timer_stop_cpu(cpu);
-                break;
-        }
-        return NOTIFY_DONE;
+        nmi_timer_start_cpu(cpu);
+        return 0;
+}
+static int nmi_timer_cpu_predown(unsigned int cpu)
+{
+        nmi_timer_stop_cpu(cpu);
+        return 0;
 }
-
-static struct notifier_block nmi_timer_cpu_nb = {
-        .notifier_call = nmi_timer_cpu_notifier
-};
 
 static int nmi_timer_start(void)
 {
@@ -103,13 +94,14 @@ static void nmi_timer_stop(void)
         put_online_cpus();
 }
 
+static enum cpuhp_state hp_online;
+
 static void nmi_timer_shutdown(void)
 {
         struct perf_event *event;
         int cpu;
 
-        cpu_notifier_register_begin();
-        __unregister_cpu_notifier(&nmi_timer_cpu_nb);
+        cpuhp_remove_state(hp_online);
         for_each_possible_cpu(cpu) {
                 event = per_cpu(nmi_timer_events, cpu);
                 if (!event)
@@ -118,13 +110,11 @@ static void nmi_timer_shutdown(void)
                 per_cpu(nmi_timer_events, cpu) = NULL;
                 perf_event_release_kernel(event);
         }
-
-        cpu_notifier_register_done();
 }
 
 static int nmi_timer_setup(void)
 {
-        int cpu, err;
+        int err;
         u64 period;
 
         /* clock cycles per tick: */
@@ -132,24 +122,14 @@ static int nmi_timer_setup(void)
         do_div(period, HZ);
         nmi_timer_attr.sample_period = period;
 
-        cpu_notifier_register_begin();
-        err = __register_cpu_notifier(&nmi_timer_cpu_nb);
-        if (err)
-                goto out;
-
-        /* can't attach events to offline cpus: */
-        for_each_online_cpu(cpu) {
-                err = nmi_timer_start_cpu(cpu);
-                if (err) {
-                        cpu_notifier_register_done();
-                        nmi_timer_shutdown();
-                        return err;
-                }
+        err = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "oprofile/nmi:online",
+                                nmi_timer_cpu_online, nmi_timer_cpu_predown);
+        if (err < 0) {
+                nmi_timer_shutdown();
+                return err;
         }
-
-out:
-        cpu_notifier_register_done();
-        return err;
+        hp_online = err;
+        return 0;
 }
 
 int __init op_nmi_timer_init(struct oprofile_operations *ops)