KVM: x86: Handle the kthread worker using the new API

Use the new API to create and destroy the "kvm-pit" kthread
worker. The API hides some implementation details.

In particular, kthread_create_worker() allocates and initializes
struct kthread_worker. It runs the kthread the right way
and stores task_struct into the worker structure.

kthread_destroy_worker() flushes all pending works, stops
the kthread and frees the structure.

This patch does not change the existing behavior except for
dynamically allocating struct kthread_worker and storing
only the pointer of this structure.

It is compile tested only because I did not find an easy
way how to run the code. Well, it should be pretty safe
given the nature of the change.

Signed-off-by: Petr Mladek <pmladek@suse.com>
Message-Id: <1476877847-11217-1-git-send-email-pmladek@suse.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/i8254.c

@@ -212,7 +212,7 @@ static void kvm_pit_ack_irq(struct kvm_irq_ack_notifier *kian)
 	 */
 	smp_mb();
 	if (atomic_dec_if_positive(&ps->pending) > 0)
-		kthread_queue_work(&pit->worker, &pit->expired);
+		kthread_queue_work(pit->worker, &pit->expired);
 }
 
 void __kvm_migrate_pit_timer(struct kvm_vcpu *vcpu)
@@ -272,7 +272,7 @@ static enum hrtimer_restart pit_timer_fn(struct hrtimer *data)
 	if (atomic_read(&ps->reinject))
 		atomic_inc(&ps->pending);
 
-	kthread_queue_work(&pt->worker, &pt->expired);
+	kthread_queue_work(pt->worker, &pt->expired);
 
 	if (ps->is_periodic) {
 		hrtimer_add_expires_ns(&ps->timer, ps->period);
@@ -667,10 +667,8 @@ struct kvm_pit *kvm_create_pit(struct kvm *kvm, u32 flags)
 	pid_nr = pid_vnr(pid);
 	put_pid(pid);
 
-	kthread_init_worker(&pit->worker);
-	pit->worker_task = kthread_run(kthread_worker_fn, &pit->worker,
-				       "kvm-pit/%d", pid_nr);
-	if (IS_ERR(pit->worker_task))
+	pit->worker = kthread_create_worker(0, "kvm-pit/%d", pid_nr);
+	if (IS_ERR(pit->worker))
 		goto fail_kthread;
 
 	kthread_init_work(&pit->expired, pit_do_work);
@@ -713,7 +711,7 @@ fail_register_speaker:
 fail_register_pit:
 	mutex_unlock(&kvm->slots_lock);
 	kvm_pit_set_reinject(pit, false);
-	kthread_stop(pit->worker_task);
+	kthread_destroy_worker(pit->worker);
 fail_kthread:
 	kvm_free_irq_source_id(kvm, pit->irq_source_id);
 fail_request:
@@ -730,8 +728,7 @@ void kvm_free_pit(struct kvm *kvm)
 		kvm_io_bus_unregister_dev(kvm, KVM_PIO_BUS, &pit->speaker_dev);
 		kvm_pit_set_reinject(pit, false);
 		hrtimer_cancel(&pit->pit_state.timer);
-		kthread_flush_work(&pit->expired);
-		kthread_stop(pit->worker_task);
+		kthread_destroy_worker(pit->worker);
 		kvm_free_irq_source_id(kvm, pit->irq_source_id);
 		kfree(pit);
 	}

arch/x86/kvm/i8254.h

@@ -44,8 +44,7 @@ struct kvm_pit {
 	struct kvm_kpit_state pit_state;
 	int irq_source_id;
 	struct kvm_irq_mask_notifier mask_notifier;
-	struct kthread_worker worker;
-	struct task_struct *worker_task;
+	struct kthread_worker *worker;
 	struct kthread_work expired;
 };