linux-kernel - Re: [PATCH 2/7] kfifo: move out spinlock

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Date:	Mon, 17 Aug 2009 09:15:24 +0100
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	Stefani Seibold <stefani@...bold.net>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Arnd Bergmann <arnd@...db.de>,
	Andi Kleen <andi@...stfloor.org>,
	Amerigo Wang <xiyou.wangcong@...il.com>,
	Joe Perches <joe@...ches.com>
Subject: Re: [PATCH 2/7] kfifo: move out spinlock

> > All over the kernel unlocked function versions have a leading _ name.
> > It's the kernel convention.
> 
> Thats is not true in every case. Have a look at list.h - That was the
> pattern i have implemented the new kfifo API.

Of course it isn't true in every case. Show me a *single* kernel
convention that is. It's also not true in no cases. foo_locked isn't used
much at all.

> The main reason to do this was to design a cleaner interface. Because
> there are very few users of this API, i thought it is a good time and
> chance to do this.
> 
> My first draft version does also not renamed this functions, but there
> was some concerns about the new functionality without modification the
> function names.
> 
> Also the remove of the spinlock made is necessary to rename the
> functions for preventing miss-use by out-of-kernel-tree drivers.

So if you didn't remove the spinlock you wouldn't have to change the API
and patch all the drivers.
 
> I think the break is not so hard if you believe. All you have to do is
> to replace or kfifo_get() into kfifo_out_locked() and kfifo_put() into
> kfifo_in_locked() if you really need the old behavior.

Which is very long winded. If you want longwinded and without breaking
stuff you can use

foo_unlocked() or unlocked_foo()

which do occur in the kernel (eg ioctl) when we want people to be
specifically aware of it although according to grep a little less often
than foo_locked() [discounting foo_is_locked which is general tests]

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