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

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Message-Id: <20090623142909.42776e75.akpm@linux-foundation.org>
Date:	Tue, 23 Jun 2009 14:29:09 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Davide Libenzi <davidel@...ilserver.org>
Cc:	linux-kernel@...r.kernel.org, avi@...hat.com, kvm@...r.kernel.org,
	ghaskins@...ell.com, rusty@...tcorp.com.au, bcrl@...ck.org
Subject: Re: [patch] eventfd - revised interface and cleanups (2nd rev)

On Tue, 23 Jun 2009 14:03:22 -0700 (PDT)
Davide Libenzi <davidel@...ilserver.org> wrote:

> 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?
> 

I think so.

> 
> > > + */
> > > +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.

You appear to have not seen the above sentence.

> > 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.

yeah, I never trust people.  You might lose the email or jump on a
plane and disappear for three weeks, then it all gets forgotten about
and lost.

If the code doesn't have any apparent showstoppers I'll often merge it
with a note that it isn't finalised.
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