Re: My system stops during startup with curretn git tree of 2.6.25-rc2

Jiri Kosina
2008-02-18T13:44:39Z

On Mon, 18 Feb 2008, Laszlo Attila Toth wrote:

> Okay, but I can't figure out what's the problem with it. I don't have
> wireless card on my linux box also I can't test it but everything else
> works. Swap is mounted. The concurrency cannot be a problem because the
> write operation is protected by a lock.

- write_lock_bh(&dev_base_lock);
- dev->link_mode = nla_get_u8(tb[IFLA_LINKMODE]);
- write_unlock_bh(&dev_base_lock);
+ if (dev->link_mode != nla_get_u8(tb[IFLA_LINKMODE])) {
+ write_lock_bh(&dev_base_lock);
+ dev->link_mode = nla_get_u8(tb[IFLA_LINKMODE]);
+ write_lock_bh(&dev_base_lock);
+ modified = 1;
+ }
}

1) you are accessing dev->link_mode and tb[] outside the dev_base_lock
2) there is obvious and immediate deadlock -- you acquire the
dev_base_lock twice, without any unlock, just look at the chunk above
3) even with this deadlock fixed, Rafael states that either NM or
wpa_supplicant (I don't recall from top of my head) still don't work

--
Jiri Kosina
SUSE Labs