linux-kernel - Re: Race free attributes in sysfs

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Message-Id: <200705202312.19191.dtor@insightbb.com>
Date:	Sun, 20 May 2007 23:12:18 -0400
From:	Dmitry Torokhov <dtor@...ightbb.com>
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 Sunday 20 May 2007 07:01, Pierre Ossman wrote:
> Hi Greg,
> 
> 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.
> 

1. dev->uevent_suppress = 1;
2. device_register(dev);
3. device_create_file(dev, ...);
4. dev->uevent_suppress = 0;
5. kobject_uevent(&dev->kobj, KOBJ_ADD);

-- 
Dmitry
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