From mboxrd@z Thu Jan  1 00:00:00 1970
From: Stephen Hemminger <shemminger@vyatta.com>
Subject: Re: a question on net_device struct
Date: Tue, 11 Aug 2009 09:12:13 -0700
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To: =?UTF-8?B?7ZmN7Iug?= shin hong <hongshin@gmail.com>
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On Tue, 11 Aug 2009 23:57:31 +0900
=ED=99=8D=EC=8B=A0 shin hong <hongshin@gmail.com> wrote:

> Hi. I have a question while I read the codes in net/core of Linux 2.6=
=2E30.4.
>=20
> 'net_device' struct defined in include/linux/netdevice.h has a field
> 'operstate'.
> Is a 'operstate' field is protected by 'dev_base_lock'?
>=20
> At set_operstate() in net/core/rtnetlink.c, it seems that dev->operst=
ate
> is protected by write_lock_bh(&dev_base_lock).
> But, in other codes, the read operations to dev->operstate are not
> consistently protected by read_lock_bh(&dev_base_lock).
>=20

Should be protected by RTNL mutex being held (see rtnl_lock() ).
The dev_base_lock is intended for the list of devices. Operations
that add and delete devices end up holding both.