Re: [PATCH] sysfs: move assignment to be under lock insysfs_remove_dir()

From: Greg KH
Date: Wed Oct 30 2013 - 18:38:46 EST

On Wed, Oct 30, 2013 at 02:41:16PM -0700, Eric W. Biederman wrote:
> One of the particularly problematic things that can happen with sysfs is
> that we can get a hotplug event in userspace and then examine sysfs and
> not find the attributes of the device because the kernel has not added
> them yet.
> Which is a particularly good reason to have a campaign against
> independent usage of device_create_file and device_remove_file in the
> device users.

I have been working on that over the past few months, there are now
default attribute groups for all things, and those are used to create
the files _before_ the hotplug event goes to userspace. I still have
more work to do to clean this up, but my goal is to remove
device_create_file() entirely, although we still have some work to go
for the platform driver case, which will take some time.

But we will get there eventually, it's a problem that has to be fixed as
more and more people hit this with multi-core, fast systems these days.

> At which point really the right thing to do when we delete a directory
> is to WARN and be very grumpy if there are any attributes in the
> directory we were removing.

We tried this once, and it was a mess. But that was a long time ago,
maybe it's better now, I'll look and see...


greg k-h
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