Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1298757

Re: debugfs_remove_recursive() while a file is in use by userspace

Show all headers | View raw

On Mon, Dec 28, 2015 at 01:11:53PM -0800, Rajat Jain wrote:
> On Mon, Dec 28, 2015 at 12:58 PM, Greg Kroah-Hartman <greg@kroah.com> wrote:
> > On Mon, Dec 28, 2015 at 12:51:32PM -0800, Rajat Jain wrote:
> >> Thanks Greg and Al for the quick turnaround.
> >>
> >> Essentially I have a device that supports something called "contexts"
> >> that can be "created" and "destroyed" during the life of the device. I
> >> want to expose some debug files for the context when it is created,
> >> and destroy the files when the context is destroyed. However, I'm not
> >> sure how do I ensure that the user is not in the middle of reading /
> >> writing / mmaping to those files. Also how do I know that user is
> >> still not holding a reference to the file structure.
> >
> > You don't.
> >
> >> It seems like debugfs is currently not a good choice for this? Would
> >> you recommend me to any other fs or subsystem that I should use for
> >> this?
> >
> > What exactly do you need to export to userspace and for what purpose?
> > For debugging-only stuff, sure, use debugfs, but don't rely on it for
> > any "real" tools, only your own debugging.
> 
> I'm actually writing a driver that would expose a "dummy device" to a
> real driver. The dummy driver relies on user space to feed in the
> device attributes (no of supported contexts etc).

That sounds "odd".

Why not configfs?

> I am now thinking that a character device interface to user space may
> actually be a better choice.

Not really, you would now have to parse things in a character driver
write() callback, not very good or robust.

> Question: Does cdev_del() ensure that all references to the file are
> dropped before it returns?

No, but when the reference is dropped, everything cleans up properly.

thanks,

greg k-h
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

debugfs_remove_recursive() while a file is in use by userspace Rajat Jain <rajatxjain@gmail.com> - 2015-12-28 21:30 +0100
  Re: debugfs_remove_recursive() while a file is in use by userspace Al Viro <viro@ZenIV.linux.org.uk> - 2015-12-28 21:40 +0100
  Re: debugfs_remove_recursive() while a file is in use by userspace Greg Kroah-Hartman <greg@kroah.com> - 2015-12-28 21:40 +0100
    Re: debugfs_remove_recursive() while a file is in use by userspace Greg Kroah-Hartman <greg@kroah.com> - 2015-12-28 22:00 +0100
      Re: debugfs_remove_recursive() while a file is in use by userspace Greg Kroah-Hartman <greg@kroah.com> - 2015-12-28 22:20 +0100
      Re: debugfs_remove_recursive() while a file is in use by userspace Rajat Jain <rajatxjain@gmail.com> - 2015-12-28 22:20 +0100
    Re: debugfs_remove_recursive() while a file is in use by userspace Rajat Jain <rajatxjain@gmail.com> - 2015-12-28 22:00 +0100
  Re: debugfs_remove_recursive() while a file is in use by userspace Nicolai Stange <nicstange@gmail.com> - 2015-12-28 21:50 +0100
    Re: debugfs_remove_recursive() while a file is in use by userspace Rajat Jain <rajatxjain@gmail.com> - 2015-12-28 22:00 +0100

csiph-web