linux-kernel - Re: Race free attributes in sysfs

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Date:	Mon, 21 May 2007 19:50:46 +0200
From:	"Kay Sievers" <kay.sievers@...y.org>
To:	"Pierre Ossman" <drzeus-list@...eus.cx>
Cc:	"Greg KH" <greg@...ah.com>, LKML <linux-kernel@...r.kernel.org>
Subject: Re: Race free attributes in sysfs

On 5/20/07, Pierre Ossman <drzeus-list@...eus.cx> wrote:
> I'm reworking the sysfs stuff in the MMC layer to be a bit more flexible, but
> there is one thing that has me baffled; how do you add attributes to an object
> in a race free manner when you have a dynamic set of attributes.
>
> I've looked at other parts of the kernel and they all use:
>
> 1. Add object.
> 2. Add attributes.
>
> To me, it seems like there's a window between 1 and 2 where the object is in
> /sys but doesn't have the proper attributes. Life for user space gets very
> annoying if it has to add artificial delays to avoid this window.
>
> So how do I do this properly? Something like this would, from my point of view,
> be the sane method:
>
> 1. Add hidden object.
> 2. Add attributes.
> 3. Show object.

Do you have a fixed set of attribute names, where you just want to
create a subset from that matches the individual device, or do you
need some sort of free naming for the attributes?

Kay
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