Subject: Re: [PATCH 02/36] scsi,rcu: convert call_rcu(fc_rport_free_rcu) to kfree_rcu()

From: Matthew Wilcox <[email-masked]>
Date: Wed, 23 Mar 2011 17:19:49 -0600

On Wed, Mar 23, 2011 at 09:05:51AM -0500, James Bottomley wrote:
> > #define kfree_rcu(ptr, rcu_head)					\
> > 	__kfree_rcu(&((ptr)->rcu_head), offsetof(typeof(*(ptr)), rcu_head))
> 
> Isn't this one of those cases where the obvious use of the interface is
> definitely wrong?

But it's a compile time breakage if you use it wrong, not runtime.

> It's also another nasty pseudo C prototype.  I know we do this sort of
> thing for container_of et al, but I don't really think we want to extend
> it.

We do it for list_entry, list_for_each_entry, etc.  And those are very
widespread within the kernel.

-- 
Matthew Wilcox				Intel Open Source Technology Centre
"Bill, look, we understand that you're interested in selling us this
operating system, but compare it to ours.  We can't possibly take such
a retrograde step."