On Tue, Aug 04, 2009 at 02:35:50PM +0200, Stanislaw Gruszka wrote: > Due to rfkill and iwlwifi mishmash of SW / HW killswitch representation, > we have race conditions which make unable turn wifi radio on, after enable > and disable again killswitch. I can observe this problem on my laptop > with iwl3945 device. > > In rfkill core HW switch and SW switch are separate 'states'. Device can > be only in one of 3 states: RFKILL_STATE_SOFT_BLOCKED, RFKILL_STATE_UNBLOCKED, > RFKILL_STATE_HARD_BLOCKED. Whereas in iwlwifi driver we have separate bits > STATUS_RF_KILL_HW and STATUS_RF_KILL_SW for HW and SW switches - radio can be > turned on, only if both bits are cleared. > > In this particular race conditions, radio can not be turned on if in driver > STATUS_RF_KILL_SW bit is set, and rfkill core is in state > RFKILL_STATE_HARD_BLOCKED, because rfkill core is unable to call > rfkill->toggle_radio(). This situation can be entered in case: > > - killswitch is turned on > - rfkill core 'see' button change first and move to RFKILL_STATE_SOFT_BLOCKED > also call ->toggle_radio() and STATE_RF_KILL_SW in driver is set > - iwl3945 get info about button from hardware to set STATUS_RF_KILL_HW bit and > force rfkill to move to RFKILL_STATE_HARD_BLOCKED > - killsiwtch is turend off > - driver clear STATUS_RF_KILL_HW > - rfkill core is unable to clear STATUS_RF_KILL_SW in driver > > Additionally call to rfkill_epo() when STATUS_RF_KILL_HW in driver is set > cause move to the same situation. > > In 2.6.31 this problem is fixed due to _total_ rewrite of rfkill subsystem. > This is a quite small fix for 2.6.30.x in iwl3945 driver. We disable > STATUS_RF_KILL_SW bit regardless of HW bit state. Also report to rfkill > subsystem SW switch bit before HW switch bit to move rfkill subsystem > to SOFT_BLOCK rather than HARD_BLOCK. > > Signed-off-by: Stanislaw Gruszka <sgruszka@xxxxxxxxxx> > --- > I'm not sure if this is good candidate for stable as this is not backport > of upstream commit. Also I did not test this patch with other iwlwifi devices, > only with iwl3945. stable is about the only place it can go, since it fixes a problem that doesn't exist in 2.6.31... John -- John W. Linville Someday the world will need a hero, and you linville@xxxxxxxxxxxxx might be all we have. Be ready. ¡Viva Honduras Libre! -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
