Re: [PATCH RFC ticketlock] v2 Auto-queued ticketlock

From: Linus Torvalds
Date: Tue Jun 11 2013 - 13:36:00 EST

Hmm. Something just struck me when reading this patch..

Our memory ordering semantics in our *current* locks are very very
subtle. We have just a "barrier()" between the

inc.head = ACCESS_ONCE(lock->tickets.head);
if (inc.head == inc.tail)
break; /* success */

and the inside of the locked region.

I think it's safe because of the new memory ordering semantics (loads
are in-order, and stores only move *down*), but there's not even a
comment about it.

So let's at least comment the current locks before making them even
more complex and subtle..

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