linux-kernel - Re: [patch] eventfd - revised interface and cleanups (2nd rev)

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Date:	Tue, 23 Jun 2009 14:03:22 -0700 (PDT)
From:	Davide Libenzi <davidel@...ilserver.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	avi@...hat.com, kvm@...r.kernel.org, ghaskins@...ell.com,
	Rusty Russell <rusty@...tcorp.com.au>,
	Benjamin LaHaise <bcrl@...ck.org>
Subject: Re: [patch] eventfd - revised interface and cleanups (2nd rev)

On Tue, 23 Jun 2009, Andrew Morton wrote:

> On Tue, 23 Jun 2009 12:25:36 -0700 (PDT)
> Davide Libenzi <davidel@...ilserver.org> wrote:
> 
> > The following patch changes the eventfd interface to de-couple the eventfd 
> > memory context, from the file pointer instance.
> > Without such change, there is no clean way to racely free handle the 
> > POLLHUP event sent when the last instance of the file* goes away.
> > Also, now the internal eventfd APIs are using the eventfd context instead 
> > of the file*.
> > Another cleanup this patch does, is making AIO select EVENTFD, instead of 
> > adding a bunch of empty function stubs inside eventfd.h in order to 
> > handle the (AIO && !EVENTFD) case.
> > 
> > ...
> >
> > +/**
> > + * eventfd_ctx_get - Acquires a reference to the internal eventfd context.
> > + * @ctx: [in] Pointer to the eventfd context.
> > + *
> > + * Returns: In case of success, returns a pointer to the eventfd context,
> > + *          otherwise a proper error code.
> 
> The description of the return value

Should functions be describing all the returned error codes, ala man pages?



> > + */
> > +struct eventfd_ctx *eventfd_ctx_get(struct eventfd_ctx *ctx)
> > +{
> > +	kref_get(&ctx->kref);
> > +	return ctx;
> > +}
> > +EXPORT_SYMBOL_GPL(eventfd_ctx_get);
> 
> doesn't match the code.
> 
> Also...
> 
> > + * Returns: A pointer to the eventfd file structure in case of success, or a
> > + *          proper error pointer in case of failure.
> 
> 
> > + * Returns: In case of success, it returns a pointer to the internal eventfd
> > + *          context, otherwise a proper error code.
> > + */
> 
> I'm unsure what the word "proper" means in this context.
> 
> The term "proper error pointer" is understandable enough - something
> you run IS_ERR() against.  "error pointer" would suffice.
> 
> But the term "proper error code" is getting a bit remote from reality.
> 
> Unfortunately the kernel doesn't have a simple and agreed-to term for
> an ERR_PTR() thingy.  Perhaps we should invent one.  "err_ptr"?

OK, but you tricked me once again :)
You posted your comments/changes while you merged the old version in -mm 
already.



- Davide


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