aha/net
Jarek Poplawski ecd2ebdea3 [AX25] af_ax25: Possible circular locking.
Bernard Pidoux F6BVP reported:
> When I killall kissattach I can see the following message.
>
> This happens on kernel 2.6.24-rc5 already patched with the 6 previously
> patches I sent recently.
>
>
> =======================================================
> [ INFO: possible circular locking dependency detected ]
> 2.6.23.9 #1
> -------------------------------------------------------
> kissattach/2906 is trying to acquire lock:
>  (linkfail_lock){-+..}, at: [<d8bd4603>] ax25_link_failed+0x11/0x39 [ax25]
>
> but task is already holding lock:
>  (ax25_list_lock){-+..}, at: [<d8bd7c7c>] ax25_device_event+0x38/0x84
> [ax25]
>
> which lock already depends on the new lock.
>
>
> the existing dependency chain (in reverse order) is:
...

lockdep is worried about the different order here:

#1 (rose_neigh_list_lock){-+..}:
#3 (ax25_list_lock){-+..}:

#0 (linkfail_lock){-+..}:
#1 (rose_neigh_list_lock){-+..}:

#3 (ax25_list_lock){-+..}:
#0 (linkfail_lock){-+..}:

So, ax25_list_lock could be taken before and after linkfail_lock. 
I don't know if this three-thread clutch is very probable (or
possible at all), but it seems another bug reported by Bernard
("[...] system impossible to reboot with linux-2.6.24-rc5")
could have similar source - namely ax25_list_lock held by
ax25_kill_by_device() during ax25_disconnect(). It looks like the
only place which calls ax25_disconnect() this way, so I guess, it
isn't necessary.

This patch is breaking the lock for ax25_disconnect().

Reported-and-tested-by: Bernard Pidoux <f6bvp@free.fr>
Signed-off-by: Jarek Poplawski <jarkao2@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2008-01-10 21:21:20 -08:00
..
9p 9p: add missing end-of-options record for trans_fd 2007-11-06 08:02:53 -06:00
802 [NET]: Move hardware header operations out of netdevice. 2007-10-10 16:52:52 -07:00
8021q [VLAN]: Fix potential race in vlan_cleanup_module vs vlan_ioctl_handler. 2007-12-11 02:45:32 -08:00
appletalk [NET]: Forget the zero_it argument of sk_alloc() 2007-11-01 00:39:31 -07:00
atm [ATM]: Check IP header validity in mpc_send_packet 2008-01-09 03:51:59 -08:00
ax25 [AX25] af_ax25: Possible circular locking. 2008-01-10 21:21:20 -08:00
bluetooth [BLUETOOTH]: put_device before device_del fix 2007-12-29 19:17:47 -08:00
bridge [BRIDGE]: Assign random address. 2007-12-16 13:35:51 -08:00
core [NEIGH]: Fix race between neigh_parms_release and neightbl_fill_parms 2008-01-10 03:48:38 -08:00
dccp [DCCP]: Spelling fixes 2007-12-20 13:59:39 -08:00
decnet [DECNET]: dn_nl_deladdr() almost always returns no error 2007-11-30 23:43:31 +11:00
econet [NET]: Forget the zero_it argument of sk_alloc() 2007-11-01 00:39:31 -07:00
ethernet [NET]: Validate device addr prior to interface-up 2007-10-23 21:27:50 -07:00
ieee80211 Merge branch 'fixes-davem' of git://git.kernel.org/pub/scm/linux/kernel/git/linville/wireless-2.6 2007-11-30 23:29:27 +11:00
ipv4 [IPV4] ROUTE: fix rcu_dereference() uses in /proc/net/rt_cache 2008-01-10 03:55:57 -08:00
ipv6 [IPV6]: IPV6_MULTICAST_IF setting is ignored on link-local connect() 2008-01-08 23:52:21 -08:00
ipx [IPX]: Use existing sock refcnt debugging infrastructure 2007-11-10 21:39:26 -08:00
irda [IRDA]: irda_create() nuke user triggable printk 2008-01-08 23:30:05 -08:00
iucv [S390] Explicitly code allocpercpu calls in iucv 2007-11-20 11:13:47 +01:00
key [IPSEC]: Avoid undefined shift operation when testing algorithm ID 2007-12-19 23:44:29 -08:00
lapb [PATCH] remove many unneeded #includes of sched.h 2007-02-14 08:09:54 -08:00
llc [NET]: Forget the zero_it argument of sk_alloc() 2007-11-01 00:39:31 -07:00
mac80211 mac80211: return an error when SIWRATE doesn't match any rate 2008-01-08 23:30:10 -08:00
netfilter [NETFILTER]: nf_conntrack_ipv4: fix module parameter compatibility 2007-12-26 19:36:33 -08:00
netlabel [NETLABEL]: Spelling fixes 2007-12-20 14:03:11 -08:00
netlink [NET]: Move unneeded data to initdata section. 2007-11-13 03:23:50 -08:00
netrom [NET]: Correct two mistaken skb_reset_mac_header() conversions. 2007-12-20 00:25:54 -08:00
packet [AF_PACKET]: Fix minor code duplication 2007-11-12 21:05:20 -08:00
rfkill rfkill: fix double-mutex-locking 2007-11-29 18:08:48 -05:00
rose [ROSE]: Trivial compilation CONFIG_INET=n case 2007-12-05 05:37:28 -08:00
rxrpc [AF_RXRPC]: Add a missing goto 2007-12-07 04:31:47 -08:00
sched [PKT_SCHED]: Spelling fixes 2007-12-20 14:02:40 -08:00
sctp [SCTP]: Add back the code that accounted for FORWARD_TSN parameter in INIT. 2008-01-08 23:30:04 -08:00
sunrpc NFS: add newline to kernel warning message in auth_gss code 2008-01-03 09:37:16 -05:00
tipc [TIPC]: Fix semaphore handling. 2007-12-14 13:54:37 -08:00
unix [UNIX]: EOF on non-blocking SOCK_SEQPACKET 2007-11-29 23:19:23 +11:00
wanrouter [NET]: Make /proc/net per network namespace 2007-10-10 16:49:06 -07:00
wireless [WIRELESS] WEXT: Fix userspace corruption on 64-bit. 2007-11-20 03:29:53 -08:00
x25 [X25]: Add missing x25_neigh_put 2008-01-04 00:47:02 -08:00
xfrm [XFRM]: xfrm_algo_clone() allocates too much memory 2008-01-08 23:39:06 -08:00
compat.c [NET]: Fix function put_cmsg() which may cause usr application memory overflow 2007-12-20 14:36:44 -08:00
Kconfig [NET]: Add network namespace clone & unshare support. 2007-10-10 16:52:46 -07:00
Makefile 9p: Reorganization of 9p file system code 2007-07-14 15:13:40 -05:00
nonet.c
socket.c [NET]: Add the helper kernel_sock_shutdown() 2007-11-12 18:10:39 -08:00
sysctl_net.c
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