On Tue, 2007-12-18 at 15:57 +0100, Johannes Berg wrote:
> Thanks. This is a bug in iwlwifi.
> 
> The problem is actually another case where my workqueue debugging with
> lockdep is triggering a warning :))
> 
> Here's the thing:
> 
> iwl3945_cancel_deferred_work does 
> 
> cancel_delayed_work_sync(&priv->init_alive_start);
> 
> (which is the "(&(&priv->init_alive_start)->work)" lock)
> 
> but it is called from within a locked section of
> mutex_lock(&priv->mutex); (locked from iwl3945_pci_suspend)
> 
> On the other hand, the task that runs from the init_alive_start
> workqueue is iwl3945_bg_init_alive_start() which will lock the same
> mutex.
> 
> So the deadlock condition is that you can be in
> cancel_delayed_work_sync() above while the mutex is locked, and be
> waiting for iwl_3945_bg_init_alive_start() which tries to lock the
> mutex.

Thanks for the analysis.

Miles, please try the attached patch. I'll send a patch for both 3945
and 4965 to linux-wireless later.

Thanks,
-yi