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

From: Alan Stern
Date: Thu May 28 2009 - 13:51:53 EST

On Thu, 28 May 2009, Eric W. Biederman wrote:

> Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> writes:
> > There's another point to consider. If you do accept my argument that
> > empty targets can be removed from visibility regardless of the host's
> > state, then this removal races with addition of a new child. Since
> > removal involves calling device_del(), it can't be protected by the
> > host lock. Instead we'd have to use a mutex to protect both target
> > addition and target removal.
> Careful. Holding a lock over device_del is an easy and hidden way
> to trigger a rare deadlocks.

Your point is well taken. In addition, I don't really like the idea of
forcing device removal to wait for some other device to be added.

I'll work around the problem somehow... A short polling loop shoud do
the job.

Alan Stern

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