smp/cfd: Convert core to hotplug state machine

Install the callbacks via the state machine. They are installed at runtime so
smpcfd_prepare_cpu() needs to be invoked by the boot-CPU.

Signed-off-by: Richard Weinberger <richard@nod.at>
[ Added the dropped CPU dying case back in. ]
Signed-off-by: Richard Cochran <rcochran@linutronix.de>
Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.de>
Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Davidlohr Bueso <dave@stgolabs>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/20160713153337.818376366@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>

4 files changed, 48 insertions, 47 deletions

diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
index 78170827a776..b5cf01ace71b 100644
--- a/include/linux/cpuhotplug.h
+++ b/include/linux/cpuhotplug.h
@@ -18,6 +18,7 @@ enum cpuhp_state {
         CPUHP_HRTIMERS_PREPARE,
         CPUHP_PROFILE_PREPARE,
         CPUHP_X2APIC_PREPARE,
+        CPUHP_SMPCFD_PREPARE,
         CPUHP_TIMERS_DEAD,
         CPUHP_NOTIFY_PREPARE,
         CPUHP_BRINGUP_CPU,
@@ -57,6 +58,7 @@ enum cpuhp_state {
         CPUHP_AP_ARM_CORESIGHT4_STARTING,
         CPUHP_AP_ARM64_ISNDEP_STARTING,
         CPUHP_AP_LEDTRIG_STARTING,
+        CPUHP_AP_SMPCFD_DYING,
         CPUHP_AP_X86_TBOOT_DYING,
         CPUHP_AP_NOTIFY_STARTING,
         CPUHP_AP_ONLINE,
diff --git a/include/linux/smp.h b/include/linux/smp.h
index c4414074bd88..eccae4690f41 100644
--- a/include/linux/smp.h
+++ b/include/linux/smp.h
@@ -196,4 +196,9 @@ extern void arch_enable_nonboot_cpus_end(void);
 
 void smp_setup_processor_id(void);
 
+/* SMP core functions */
+int smpcfd_prepare_cpu(unsigned int cpu);
+int smpcfd_dead_cpu(unsigned int cpu);
+int smpcfd_dying_cpu(unsigned int cpu);
+
 #endif /* __LINUX_SMP_H */
diff --git a/kernel/cpu.c b/kernel/cpu.c
index e1017d92d308..008e2fd40cb1 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -1195,6 +1195,11 @@ static struct cpuhp_step cpuhp_bp_states[] = {
                 .startup = hrtimers_prepare_cpu,
                 .teardown = hrtimers_dead_cpu,
         },
+        [CPUHP_SMPCFD_PREPARE] = {
+                .name = "SMPCFD prepare",
+                .startup = smpcfd_prepare_cpu,
+                .teardown = smpcfd_dead_cpu,
+        },
         [CPUHP_TIMERS_DEAD] = {
                 .name = "timers dead",
                 .startup = NULL,
@@ -1218,6 +1223,10 @@ static struct cpuhp_step cpuhp_bp_states[] = {
                 .teardown               = NULL,
                 .cant_stop              = true,
         },
+        [CPUHP_AP_SMPCFD_DYING] = {
+                .startup = NULL,
+                .teardown = smpcfd_dying_cpu,
+        },
         /*
          * Handled on controll processor until the plugged processor manages
          * this itself.
diff --git a/kernel/smp.c b/kernel/smp.c
index 74165443c240..7180491c9678 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -33,69 +33,54 @@ static DEFINE_PER_CPU_SHARED_ALIGNED(struct llist_head, call_single_queue);
 
 static void flush_smp_call_function_queue(bool warn_cpu_offline);
 
-static int
-hotplug_cfd(struct notifier_block *nfb, unsigned long action, void *hcpu)
+int smpcfd_prepare_cpu(unsigned int cpu)
 {
-        long cpu = (long)hcpu;
         struct call_function_data *cfd = &per_cpu(cfd_data, cpu);
 
-        switch (action) {
-        case CPU_UP_PREPARE:
-        case CPU_UP_PREPARE_FROZEN:
-                if (!zalloc_cpumask_var_node(&cfd->cpumask, GFP_KERNEL,
-                                cpu_to_node(cpu)))
-                        return notifier_from_errno(-ENOMEM);
-                cfd->csd = alloc_percpu(struct call_single_data);
-                if (!cfd->csd) {
-                        free_cpumask_var(cfd->cpumask);
-                        return notifier_from_errno(-ENOMEM);
-                }
-                break;
-
-#ifdef CONFIG_HOTPLUG_CPU
-        case CPU_UP_CANCELED:
-        case CPU_UP_CANCELED_FROZEN:
-                /* Fall-through to the CPU_DEAD[_FROZEN] case. */
-
-        case CPU_DEAD:
-        case CPU_DEAD_FROZEN:
+        if (!zalloc_cpumask_var_node(&cfd->cpumask, GFP_KERNEL,
+                                     cpu_to_node(cpu)))
+                return -ENOMEM;
+        cfd->csd = alloc_percpu(struct call_single_data);
+        if (!cfd->csd) {
                 free_cpumask_var(cfd->cpumask);
-                free_percpu(cfd->csd);
-                break;
+                return -ENOMEM;
+        }
 
-        case CPU_DYING:
-        case CPU_DYING_FROZEN:
-                /*
-                 * The IPIs for the smp-call-function callbacks queued by other
-                 * CPUs might arrive late, either due to hardware latencies or
-                 * because this CPU disabled interrupts (inside stop-machine)
-                 * before the IPIs were sent. So flush out any pending callbacks
-                 * explicitly (without waiting for the IPIs to arrive), to
-                 * ensure that the outgoing CPU doesn't go offline with work
-                 * still pending.
-                 */
-                flush_smp_call_function_queue(false);
-                break;
-#endif
-        };
+        return 0;
+}
+
+int smpcfd_dead_cpu(unsigned int cpu)
+{
+        struct call_function_data *cfd = &per_cpu(cfd_data, cpu);
 
-        return NOTIFY_OK;
+        free_cpumask_var(cfd->cpumask);
+        free_percpu(cfd->csd);
+        return 0;
 }
 
-static struct notifier_block hotplug_cfd_notifier = {
-        .notifier_call          = hotplug_cfd,
-};
+int smpcfd_dying_cpu(unsigned int cpu)
+{
+        /*
+         * The IPIs for the smp-call-function callbacks queued by other
+         * CPUs might arrive late, either due to hardware latencies or
+         * because this CPU disabled interrupts (inside stop-machine)
+         * before the IPIs were sent. So flush out any pending callbacks
+         * explicitly (without waiting for the IPIs to arrive), to
+         * ensure that the outgoing CPU doesn't go offline with work
+         * still pending.
+         */
+        flush_smp_call_function_queue(false);
+        return 0;
+}
 
 void __init call_function_init(void)
 {
-        void *cpu = (void *)(long)smp_processor_id();
         int i;
 
         for_each_possible_cpu(i)
                 init_llist_head(&per_cpu(call_single_queue, i));
 
-        hotplug_cfd(&hotplug_cfd_notifier, CPU_UP_PREPARE, cpu);
-        register_cpu_notifier(&hotplug_cfd_notifier);
+        smpcfd_prepare_cpu(smp_processor_id());
 }
 
 /*