netdev - Re: IPv4/IPv6 sysctl unregistration deadlock

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Message-ID: <20090226122450.6d27eec6@nehalam>
Date:	Thu, 26 Feb 2009 12:24:50 -0800
From:	Stephen Hemminger <shemminger@...tta.com>
To:	ebiederm@...ssion.com (Eric W. Biederman)
Cc:	Herbert Xu <herbert@...dor.apana.org.au>,
	Patrick McHardy <kaber@...sh.net>,
	Linux Netdev List <netdev@...r.kernel.org>,
	"David S. Miller" <davem@...emloft.net>
Subject: Re: IPv4/IPv6 sysctl unregistration deadlock

On Thu, 26 Feb 2009 11:01:41 -0800
ebiederm@...ssion.com (Eric W. Biederman) wrote:

> Stephen Hemminger <shemminger@...tta.com> writes:
> 
> > What about something like this:
> >
> > Subject: [PATCH] Avoid race between network down and sysfs
> 
> As far as solutions go.  That looks like the easiest correct solution.
> So.  
> Acked-by: "Eric W. Biederman" <ebiederm@...ssion.com>
> 
> 
> Will -ERESTARTSYS trigger the in kernel restart logic in this case?
> 
> There are a lot more cases to cover, and I don't I like it long
> term.  Spinning waiting for rtnl_lock feels wrong.  Plus it does
> not help with discovering the problem in new sysfs, sysctl, or
> proc files.
> 
> It has the major advantage that we can fix things now.
> 

I haven't tested it, but it should restart in VFS.
Spinning is not that big a deal, and it also handles the case
where the name changed or some other race occurred during processing.
When syscall is re-entered, the name will no longer be found and
-ENOENT will be returned.
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