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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> |
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