netdev - Re: [PATCH] HDLC driver: use unregister_netdev instead of unregister

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Message-ID: <m3ve71t194.fsf@maximus.localdomain>
Date:	Fri, 14 Dec 2007 22:28:07 +0100
From:	Krzysztof Halasa <khc@...waw.pl>
To:	Wang Chen <wangchen@...fujitsu.com>
Cc:	Jeff Garzik <jgarzik@...ox.com>, netdev@...r.kernel.org,
	"David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH] HDLC driver: use unregister_netdev instead of unregister_netdevice

Wang Chen <wangchen@...fujitsu.com> writes:

> [PATCH] HDLC driver: use unregister_netdev instead of unregister_netdevice
>
> Since the caller and the upper caller doesn't hod the rtnl semaphore.
> We should use unregister_netdev instead of unregister_netdevice.

NAK, not-a-bug. The caller actually holds rtnl, it goes through
the netdev core ioctl dispatcher:

(unregister_netdevice+0x0/0x24) from (fr_ioctl+0x688/0x75c)
/* fr_del_pvc() and fr_add_pvc() optimized out by gcc */
(fr_ioctl+0x0/0x75c) from (hdlc_ioctl+0x4c/0x8c)
(hdlc_ioctl+0x0/0x8c) from (hss_ioctl+0x3c/0x324)
(hss_ioctl+0x0/0x324) from (dev_ifsioc+0x428/0x4e8)
(dev_ifsioc+0x0/0x4e8) from (dev_ioctl+0x5d8/0x664)
(dev_ioctl+0x0/0x664) from (sock_ioctl+0x90/0x254)
(sock_ioctl+0x0/0x254) from (do_ioctl+0x34/0x78)
(do_ioctl+0x0/0x78) from (vfs_ioctl+0x78/0x2a8)
(vfs_ioctl+0x0/0x2a8) from (sys_ioctl+0x40/0x64)
(sys_ioctl+0x0/0x64) from (ret_fast_syscall+0x0/0x2c)

The patch would make it deadlock.

Please note that sister fr_add_pvc() uses register_netdevice().
The same applies to fr_destroy().
-- 
Krzysztof Halasa
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