evl/observable: convert observable, subscriber locks to hard locks

The subscriber lock is shared between both execution stages, but
accessed from the in-band stage for the most part, which implies
disabling hard irqs while holding it. Meanwhile, out-of-band IRQs and
EVL threads may compete for the observable lock, which would require
hard irqs to be disabled while holding it.  Therefore we would not
generally benefit from the preemption disabling feature we are going
to add to the EVL-specific spinlock in any case. Make these hard locks
to clarify the intent.
Signed-off-by: Philippe Gerum <rpm@xenomai.org>

include/evl/observable.h

@@ -27,7 +27,7 @@ struct evl_observable {
 	struct evl_poll_head poll_head;
 	struct irq_work wake_irqwork;
 	struct irq_work flush_irqwork;
-	evl_spinlock_t lock;		/* guards observers and flush_list */
+	hard_spinlock_t lock;		/* guards observers and flush_list */
 	u32 serial_counter;
 	int writable_observers;
 };

kernel/evl/observable.c

@@ -30,7 +30,7 @@
  */
 struct evl_subscriber {
   	struct rb_root subscriptions; /* struct evl_observer */
-	evl_spinlock_t lock;
+	hard_spinlock_t lock;
 };
 
 struct evl_notification_record {
@@ -133,7 +133,7 @@ static int add_subscription(struct evl_observable *observable,
 		sbr = kzalloc(sizeof(*sbr), GFP_KERNEL);
 		if (sbr == NULL)
 			return -ENOMEM;
-		evl_spin_lock_init(&sbr->lock);
+		raw_spin_lock_init(&sbr->lock);
 		sbr->subscriptions = RB_ROOT;
 		evl_set_subscriber(sbr);
 	}
@@ -169,9 +169,9 @@ static int add_subscription(struct evl_observable *observable,
 	if (op_flags & EVL_NOTIFY_ONCHANGE)
 		observer->flags |= EVL_NOTIFY_INITIAL;
 
-	evl_spin_lock_irqsave(&sbr->lock, flags);
+	raw_spin_lock_irqsave(&sbr->lock, flags);
 	ret = index_observer(&sbr->subscriptions, observer);
-	evl_spin_unlock_irqrestore(&sbr->lock, flags);
+	raw_spin_unlock_irqrestore(&sbr->lock, flags);
 	if (ret)
 		goto dup_subscription;
 
@@ -187,12 +187,12 @@ static int add_subscription(struct evl_observable *observable,
 	 * (FIFO) in case users make such assumption for master mode
 	 * (which undergoes round-robin).
 	 */
-	evl_spin_lock_irqsave(&observable->lock, flags);
+	raw_spin_lock_irqsave(&observable->lock, flags);
 	list_add_tail(&observer->next, &observable->observers);
 	raw_spin_lock(&observable->oob_wait.lock);
 	observable->writable_observers++;
 	raw_spin_unlock(&observable->oob_wait.lock);
-	evl_spin_unlock_irqrestore(&observable->lock, flags);
+	raw_spin_unlock_irqrestore(&observable->lock, flags);
 	evl_signal_poll_events(&observable->poll_head, POLLOUT|POLLWRNORM);
 
 	evl_put_element(&observable->element);
@@ -248,7 +248,7 @@ static bool detach_observer(struct evl_observer *observer,
 	bool dropped = false;
 	unsigned long flags;
 
-	evl_spin_lock_irqsave(&observable->lock, flags);
+	raw_spin_lock_irqsave(&observable->lock, flags);
 
 	/*
 	 * If the refcount does not drop to zero, push_notification()
@@ -259,7 +259,7 @@ static bool detach_observer(struct evl_observer *observer,
 		dropped = true;
 	}
 
-	evl_spin_unlock_irqrestore(&observable->lock, flags);
+	raw_spin_unlock_irqrestore(&observable->lock, flags);
 
 	return dropped;
 }
@@ -290,9 +290,9 @@ static int cancel_subscription(struct evl_observable *observable) /* in-band */
 	 * this observer escapes evl_drop_subscriptions() in case the
 	 * caller exits afterwards.
 	 */
-	evl_spin_lock_irqsave(&sbr->lock, flags);
+	raw_spin_lock_irqsave(&sbr->lock, flags);
 	rb_erase(&observer->rb, &sbr->subscriptions);
-	evl_spin_unlock_irqrestore(&sbr->lock, flags);
+	raw_spin_unlock_irqrestore(&sbr->lock, flags);
 
 	/*
 	 * Remove observer from observable->observers. Subscription
@@ -429,17 +429,17 @@ static void do_flush_work(struct evl_observable *observable)
 	 * only rarely, in case push_notification() raced with
 	 * cancel_subscription() or evl_drop_subscriptions().
 	 */
-	evl_spin_lock_irqsave(&observable->lock, flags);
+	raw_spin_lock_irqsave(&observable->lock, flags);
 
 	while (!list_empty(&observable->flush_list)) {
 		observer = list_get_entry(&observable->flush_list,
 					struct evl_observer, next);
-		evl_spin_unlock_irqrestore(&observable->lock, flags);
+		raw_spin_unlock_irqrestore(&observable->lock, flags);
 		kfree(observer);
-		evl_spin_lock_irqsave(&observable->lock, flags);
+		raw_spin_lock_irqsave(&observable->lock, flags);
 	}
 
-	evl_spin_unlock_irqrestore(&observable->lock, flags);
+	raw_spin_unlock_irqrestore(&observable->lock, flags);
 }
 
 static void inband_flush_irqwork(struct irq_work *work)
@@ -499,7 +499,7 @@ static bool notify_single(struct evl_observable *observable,
 	bool do_flush = false;
 	unsigned long flags;
 
-	evl_spin_lock_irqsave(&observable->lock, flags);
+	raw_spin_lock_irqsave(&observable->lock, flags);
 
 	if (list_empty(&observable->observers))
 		goto out;
@@ -519,12 +519,12 @@ static bool notify_single(struct evl_observable *observable,
 		list_add_tail(&observer->next, &observable->observers);
 	}
 
-	evl_spin_unlock_irqrestore(&observable->lock, flags);
+	raw_spin_unlock_irqrestore(&observable->lock, flags);
 
 	if (notify_one_observer(observable, observer, nfr))
 		*len_r += sizeof(struct evl_notice);
 
-	evl_spin_lock_irqsave(&observable->lock, flags);
+	raw_spin_lock_irqsave(&observable->lock, flags);
 
 	if (unlikely(put_observer(observer))) {
 		detach_observer_locked(observer, observable);
@@ -532,7 +532,7 @@ static bool notify_single(struct evl_observable *observable,
 		do_flush = true;
 	}
 out:
-	evl_spin_unlock_irqrestore(&observable->lock, flags);
+	raw_spin_unlock_irqrestore(&observable->lock, flags);
 
 	return do_flush;
 }
@@ -546,7 +546,7 @@ static bool notify_all(struct evl_observable *observable,
 	unsigned long flags;
 	bool do_flush;
 
-	evl_spin_lock_irqsave(&observable->lock, flags);
+	raw_spin_lock_irqsave(&observable->lock, flags);
 
 	if (list_empty(&observable->observers)) {
 		do_flush = false;
@@ -578,12 +578,12 @@ static bool notify_all(struct evl_observable *observable,
 
 		observer = list_entry(pos, struct evl_observer, next);
 
-		evl_spin_unlock_irqrestore(&observable->lock, flags);
+		raw_spin_unlock_irqrestore(&observable->lock, flags);
 
 		if (notify_one_observer(observable, observer, nfr))
 			*len_r += sizeof(struct evl_notice);
 
-		evl_spin_lock_irqsave(&observable->lock, flags);
+		raw_spin_lock_irqsave(&observable->lock, flags);
 
 		if (unlikely(put_observer(observer))) {
 			detach_observer_locked(observer, observable);
@@ -593,7 +593,7 @@ static bool notify_all(struct evl_observable *observable,
 
 	do_flush = !list_empty(&observable->flush_list);
 out:
-	evl_spin_unlock_irqrestore(&observable->lock, flags);
+	raw_spin_unlock_irqrestore(&observable->lock, flags);
 
 	return do_flush;
 }
@@ -1103,7 +1103,7 @@ struct evl_observable *evl_alloc_observable(const char __user *u_name,
 	init_irq_work(&observable->wake_irqwork, inband_wake_irqwork);
 	init_irq_work(&observable->flush_irqwork, inband_flush_irqwork);
 	evl_init_poll_head(&observable->poll_head);
-	evl_spin_lock_init(&observable->lock);
+	raw_spin_lock_init(&observable->lock);
 	evl_index_factory_element(&observable->element);
 
 	return observable;