netdev - Re: [PATCH] rtnl: Simplify ASSERT

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Date:	Sat, 29 Sep 2007 12:31:14 +0800
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	ebiederm@...ssion.com (Eric W. Biederman)
Cc:	davem@...emloft.net, netdev@...r.kernel.org
Subject: Re: [PATCH] rtnl: Simplify ASSERT_RTNL

Eric W. Biederman <ebiederm@...ssion.com> wrote:
> 
> Currently we have the call path:
> macvlan_open -> dev_unicast_add -> __dev_set_rx_mode ->
>        __dev_set_promiscuity -> ASSERT_RTNL -> mutex_trylock
> 
> When mutex debugging is on taking a mutex complains if we are not
> allowed to sleep.  At that point we have called netif_tx_lock_bh
> so we are clearly not allowed to sleep.  Arguably this is not a
> problem for mutex_trylock.

Actually holding the TX lock here is a bug.  We're going to
call down into the hardware with __dev_set_promiscuity, which
may sleep (think USB NICs), so we definitely shouldn't be holding
any spin locks.

Patrick, could we avoid taking the TX lock here somehow?

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