linux-kernel - Re: [take12 1/3] kevent: Core files.

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Date:	Wed, 23 Aug 2006 10:51:36 +0200
From:	Eric Dumazet <dada1@...mosbay.com>
To:	Evgeniy Polyakov <johnpol@....mipt.ru>
Cc:	lkml <linux-kernel@...r.kernel.org>,
	David Miller <davem@...emloft.net>,
	Ulrich Drepper <drepper@...hat.com>,
	Andrew Morton <akpm@...l.org>, netdev <netdev@...r.kernel.org>,
	Zach Brown <zach.brown@...cle.com>,
	Christoph Hellwig <hch@...radead.org>
Subject: Re: [take12 1/3] kevent: Core files.

Hello Evgeniy

I have one comment/suggestion (minor detail, your work is very good)

I suggest to add one item in kevent_registered_callbacks[], so that 
kevent_registered_callbacks[KEVENT_MAX] is valid and can act as a fallback.

In kevent_add_callbacks() you could replace the eventual NULL pointers by 
kevent_break() in 
kevent_registered_callbacks[pos].{callback, enqueue, dequeue}
like :

+int kevent_add_callbacks(const struct kevent_callbacks *cb, unsigned int pos)
+{
+	struct kevent_callbacks *p = &kevent_registered_callbacks[pos];
+       if (pos >= KEVENT_MAX)
+               return -EINVAL;
+      p->enqueue = (cb->enqueue) ? cb->enqueue : kevent_break;
+      p->dequeue = (cb->dequeue) ? cb->dequeue : kevent_break;
+      p->callback = (cb->callback) ? cb->callback : kevent_break;
+       printk(KERN_INFO "KEVENT: Added callbacks for type %u.\n", pos);
+       return 0;
+}

(I also added a const qualifier in first function argument, and unsigned int 
pos so that the "if (pos >= KEVENT_MAX)" test catches 'negative' values)

Then you change kevent_break() to return -EINVAL instead of 0.

+int kevent_break(struct kevent *k)
+{
+       unsigned long flags;
+
+       spin_lock_irqsave(&k->ulock, flags);
+       k->event.ret_flags |= KEVENT_RET_BROKEN;
+       spin_unlock_irqrestore(&k->ulock, flags);
+       return -EINVAL;
+}

Then avoid the tests in kevent_enqueue()

+int kevent_enqueue(struct kevent *k)
+{
+       return k->callbacks.enqueue(k);
+}

And avoid the tests in  kevent_dequeue()

+int kevent_dequeue(struct kevent *k)
+{
+       return k->callbacks.dequeue(k);
+}

And change kevent_init() to

+int kevent_init(struct kevent *k)
+{
+       spin_lock_init(&k->ulock);
+       k->flags = 0;
+
+       if (unlikely(k->event.type >= KEVENT_MAX))
+               k->event.type = KEVENT_MAX;
+	 
+
+       k->callbacks = kevent_registered_callbacks[k->event.type];
+       if (unlikely(k->callbacks.callback == kevent_break))
+               return kevent_break(k);
+
+       return 0;
+}



Eric Dumazet
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