On Wed, 22 Sep 2010 16:39:57 +0200
Johannes Berg <johannes@xxxxxxxxxxxxxxxx> wrote:
> On Wed, 2010-09-22 at 10:57 +0200, Stanislaw Gruszka wrote:
>
> > So why we can see this warning? During my testing I saw it also.
> > There is race regarding SCAN_HW_SCANNING bit, usually we set/clear
> > this bit under local->mtx, but not in ieee80211_restart_hw()
> >
> > cpu0 cpu1
> > __ieee80211_start_scan
> > __set_bit(SCAN_HW_SCANNING, &local->scanning);
> >
> > iwl_bg_restart()
> > ieee80211_restart_hw()
> > WARN
>
> Why can't iwlwifi's bg_restart() force-abort the scan? It'll be aborted
> anyway...
Yes, bg_restart() force scan abort, but not if no scan is pending. It looks
like that:
cpu0 cpu1
iwl_bg_restart()
__iwl_down()
iwl_scan_cancel_timeout
(do nothing since no pending scan)
__ieee80211_start_scan
__set_bit(SCAN_HW_SCANNING, &local->scanning);
ieee80211_restart_hw()
WARN
drv_hw_scan
iwl_mac_hw_scan
(OK, fail new scan, return error)
local->scanning = 0;
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