Re: [PATCH 25/20] sysfs: Only support removing emtpy sysfs directories.

[Alan Stern]

On Wed, 27 May 2009, Eric W. Biederman wrote:

> Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> writes:
> 
> > On Wed, 27 May 2009, Kay Sievers wrote:
> >
> >> On Wed, May 27, 2009 at 01:49, James Bottomley
> >> <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx> wrote:
> >> 
> >> > OK ... perhaps we have to wait a little harder: try this; it waits until
> >> > all the targets have disappeared from visibility via an event.
> >> 
> >> That seems to work fine here.
> >
> > It's good for a short-term fix.  For the longer term, I still think 
> > it's a mistake to wait for the sdevs to be released before deleting the 
> > target.  It gives user programs the ability to block the host-removal 
> > thread indefinitely.
> 
> How can user programs block removal indefinitely today?

As fas as I know, they can't.  Instead, they can cause the SCSI layer 
to unregister a sysfs directory containing a child directory.  :-)

Basically, a user program can delay removal of the child (i.e., the
target) directory indefinitely, because currently the target isn't
unregistered when all its children are removed -- it's unregistered
when all its children are _released_.

Alan Stern

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