From mboxrd@z Thu Jan  1 00:00:00 1970
From: ebiederm@xmission.com (Eric W. Biederman)
Subject: Re: IPv4/IPv6 sysctl unregistration deadlock
Date: Thu, 26 Feb 2009 11:01:41 -0800
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Cc: Herbert Xu <herbert@gondor.apana.org.au>,
	Patrick McHardy <kaber@trash.net>,
	Linux Netdev List <netdev@vger.kernel.org>,
	"David S. Miller" <davem@davemloft.net>
To: Stephen Hemminger <shemminger@vyatta.com>
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In-Reply-To: <20090226084924.16cb3e08@nehalam> (Stephen Hemminger's message of "Thu\, 26 Feb 2009 08\:49\:24 -0800")
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Stephen Hemminger <shemminger@vyatta.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@xmission.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.

> Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
>
> --- a/net/core/net-sysfs.c	2009-02-26 08:36:18.000000000 -0800
> +++ b/net/core/net-sysfs.c	2009-02-26 08:37:51.000000000 -0800
> @@ -77,7 +77,9 @@ static ssize_t netdev_store(struct devic
>  	if (endp == buf)
>  		goto err;
>  
> -	rtnl_lock();
> +	if (!rtnl_trylock())
> +		return -ERESTARTSYS;
> +
>  	if (dev_isalive(net)) {
>  		if ((ret = (*set)(net, new)) == 0)
>  			ret = len;