Hi James,

On 9/19/20 2:13 AM, James Morse wrote:

On 30/07/2020 02:45, Gavin Shan wrote:

quoted

This removes the unnecessary while loop in sdei_event_register().

Did you notice how this code doesn't need to unwind anything to clean up?
It only unlocks the mutex, and the indentation tells you it always does that.

Yes, I noticed it.

quoted

This shouldn't cause any functional changes.

Why is it better? This complicates the flow by jumping around with goto.

If the unwinding were necessary, I agree this would be clearer, but as its not ... why do
we need to make this harder to read?

I intended to avoid the unnecessary nested statements, caused
by the "do { ... } while (0)". With that, the code looks a bit
cleaner. It might make the code a bit harder to read, but it's
fine to me. Besides, the unnecessary "do { ... } while (0)" looks
a bit strange to me because the block is executed for once.

So I think it'd better to keep the changes if you don't object
strongly. Otherwise, I can drop this one.

Cheers,
Gavin

quoted

diff --git a/drivers/firmware/arm_sdei.c b/drivers/firmware/arm_sdei.c
index 03b1179da9b4..d04329f98922 100644
--- a/drivers/firmware/arm_sdei.c
+++ b/drivers/firmware/arm_sdei.c

@@ -590,36 +590,34 @@ int sdei_event_register(u32 event_num, sdei_event_callback *cb, void *arg)
  	WARN_ON(in_nmi());
  
  	mutex_lock(&sdei_events_lock);
-	do {
-		if (sdei_event_find(event_num)) {
-			pr_warn("Event %u already registered\n", event_num);
-			err = -EBUSY;
-			break;
-		}
+	if (sdei_event_find(event_num)) {
+		pr_warn("Event %u already registered\n", event_num);
+		err = -EBUSY;
+		goto unlock;
+	}
  
-		event = sdei_event_create(event_num, cb, arg);
-		if (IS_ERR(event)) {
-			err = PTR_ERR(event);
-			pr_warn("Failed to create event %u: %d\n", event_num,
-				err);
-			break;
-		}
+	event = sdei_event_create(event_num, cb, arg);
+	if (IS_ERR(event)) {
+		err = PTR_ERR(event);
+		pr_warn("Failed to create event %u: %d\n", event_num, err);
+		goto unlock;
+	}
  
-		cpus_read_lock();
-		err = _sdei_event_register(event);
-		if (err) {
-			sdei_event_destroy(event);
-			pr_warn("Failed to register event %u: %d\n", event_num,
-				err);
-		} else {
-			spin_lock(&sdei_list_lock);
-			event->reregister = true;
-			spin_unlock(&sdei_list_lock);
-		}
-		cpus_read_unlock();
-	} while (0);
-	mutex_unlock(&sdei_events_lock);
+	cpus_read_lock();
+	err = _sdei_event_register(event);
+	if (err) {
+		sdei_event_destroy(event);
+		pr_warn("Failed to register event %u: %d\n", event_num, err);
+		goto cpu_unlock;
+	}
  
+	spin_lock(&sdei_list_lock);
+	event->reregister = true;
+	spin_unlock(&sdei_list_lock);
+cpu_unlock:
+	cpus_read_unlock();
+unlock:
+	mutex_unlock(&sdei_events_lock);
  	return err;
  }
  

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel