kernel/softirq: Convert to hotplug state machine

Install the callbacks via the state machine.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/20160818125731.27256-7-bigeasy@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

2 files changed, 7 insertions, 21 deletions

diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
index 854e59a426d4..a421407a317f 100644
--- a/include/linux/cpuhotplug.h
+++ b/include/linux/cpuhotplug.h
@@ -17,6 +17,7 @@ enum cpuhp_state {
         CPUHP_VIRT_NET_DEAD,
         CPUHP_SLUB_DEAD,
         CPUHP_MM_WRITEBACK_DEAD,
+        CPUHP_SOFTIRQ_DEAD,
         CPUHP_WORKQUEUE_PREP,
         CPUHP_POWER_NUMA_PREPARE,
         CPUHP_HRTIMERS_PREPARE,
diff --git a/kernel/softirq.c b/kernel/softirq.c
index 17caf4b63342..c372114494f5 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -700,7 +700,7 @@ void tasklet_kill_immediate(struct tasklet_struct *t, unsigned int cpu)
         BUG();
 }
 
-static void takeover_tasklets(unsigned int cpu)
+static int takeover_tasklets(unsigned int cpu)
 {
         /* CPU is dead, so no lock needed. */
         local_irq_disable();
@@ -723,27 +723,12 @@ static void takeover_tasklets(unsigned int cpu)
         raise_softirq_irqoff(HI_SOFTIRQ);
 
         local_irq_enable();
+        return 0;
 }
+#else
+#define takeover_tasklets       NULL
 #endif /* CONFIG_HOTPLUG_CPU */
 
-static int cpu_callback(struct notifier_block *nfb, unsigned long action,
-                        void *hcpu)
-{
-        switch (action) {
-#ifdef CONFIG_HOTPLUG_CPU
-        case CPU_DEAD:
-        case CPU_DEAD_FROZEN:
-                takeover_tasklets((unsigned long)hcpu);
-                break;
-#endif /* CONFIG_HOTPLUG_CPU */
-        }
-        return NOTIFY_OK;
-}
-
-static struct notifier_block cpu_nfb = {
-        .notifier_call = cpu_callback
-};
-
 static struct smp_hotplug_thread softirq_threads = {
         .store                  = &ksoftirqd,
         .thread_should_run      = ksoftirqd_should_run,
@@ -753,8 +738,8 @@ static struct smp_hotplug_thread softirq_threads = {
 
 static __init int spawn_ksoftirqd(void)
 {
-        register_cpu_notifier(&cpu_nfb);
-
+        cpuhp_setup_state_nocalls(CPUHP_SOFTIRQ_DEAD, "softirq:dead", NULL,
+                                  takeover_tasklets);
         BUG_ON(smpboot_register_percpu_thread(&softirq_threads));
 
         return 0;