netdev - Re: [1/2] tun: Only free a netdev when all tun descriptors are closed

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Message-ID: <20090424121156.GA28039@gondor.apana.org.au>
Date:	Fri, 24 Apr 2009 20:11:56 +0800
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	Christian Borntraeger <borntraeger@...ibm.com>
Cc:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Patrick McHardy <kaber@...sh.net>,
	Matias Zabaljauregui <zabaljauregui@...il.com>, odie@...aau.dk,
	Rusty Russell <rusty@...tcorp.com.au>, lguest@...abs.org,
	virtualization@...ts.osdl.org,
	"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
	Carsten Otte <cotte@...ibm.com>
Subject: Re: [1/2] tun: Only free a netdev when all tun descriptors are
	closed

On Fri, Apr 24, 2009 at 10:55:49AM +0200, Christian Borntraeger wrote:
> Am Thursday 16 April 2009 13:08:18 schrieb Herbert Xu:
>
> > Here's the patch.  I'd appreciate if everyone can review it
> > and see if they can recreate the original race by
> > 
> > 1) Starting a process using tun and polls on it;
> > 2) Doing ip tun del tunXXX while the process is polling.
> > 
> > tun: Only free a netdev when all tun descriptors are closed
> > 
> > The commit c70f182940f988448f3c12a209d18b1edc276e33 ("tun: Fix
> > races between tun_net_close and free_netdev") fixed a race where
> > an asynchronous deletion of a tun device can hose a poll(2) on
> > a tun fd attached to that device.
> 
> Sorry for the late reply, but this patch creates another regression:
> Now TUNSETIFF returns EBUSY on a persistent tap device:
> 
> open("/dev/net/tun", O_RDWR) = 11
> ioctl(11, 0x400454ca, 0x3ffff8e2270) = -1 EBUSY (Device or resource busy)

The patch you qouted has been superceded by many versions :)

Can you please test the latest that's in davem's tree?

Thanks,
-- 
Visit Openswan at http://www.openswan.org/
Email: Herbert Xu ~{PmV>HI~} <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
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