Re: [PATCH w-t] iwlwifi: rewrite iwl-scan.c to avoid race conditions

[Stanislaw Gruszka <sgruszka@redhat.com>]

On Wed, Sep 01, 2010 at 04:26:44PM +0200, Johannes Berg wrote:
> Ah, but Tejun will kill us if we add more workqueues to the current
> kernel :-)

Ok, I wanna live ...

> > > > For sure abort_scan and abort_timeout works have to be scheduled on something
> > > > other than priv->workqueue. I'm queuing all scan works on priv->scan_workqueue
> > > > for consistency.
> > > 
> > > Remind me: The reason is that we need to cancel them from within the
> > > workqueue? But if we're on the same workqueue, it seems like they
> > > couldn't be running already, so cancel_work_sync() would always cancel
> > > them? 
> > 
> > Problem is not canceling, but exactly that we can not run new work when
> > old one does not finish. For example, if queued to priv->workqueue
> > abort_timeout will not be able run when we are performing iwl_bg_restart.
> > Will run after iwl_bg_restart finish, we don't want that.
> 
> Ok ... Not sure I understand. Why do we care about abort_timeout work
> coming after it? We'd cancel it anyway, when we kill the scan from
> bg_restart, no?

I wanted abort_timeout finish to avoid warning I putted in
iwl_scan_cancel_sleep, but I could just remove the warning ...

Cancel at the end of iwl_cancel_scan_deferred_work() is for case
when we still get notification from f/w and clear STATUS_SCAN_HW bit in 
iwl_rx_scan_complete_notif. This can happen when firmware is in some
sane state but we do restart (for example: when debugfs force_reset
file was used).

For the same reason we need have to iwl_bg_scan_completed allow to run
in parallel with iwl_bg_restart. To complete scanning when performing
restart, but f/w is responsible.

Stanislaw