On Tue, Jan 07, 2014 at 12:28:26PM -0600, Larry Finger wrote: > rtnl_mutex --> misc_mtx --> rfkill_global_mutex > > Possible unsafe locking scenario: > > CPU0 CPU1 > ---- ---- > lock(rfkill_global_mutex); > lock(misc_mtx); > lock(rfkill_global_mutex); > lock(rtnl_mutex); > > *** DEADLOCK *** There are 3 mutexes dependency. The deadlock can happen if on another cpu, let say CPU2, there will be sequence: lock(rtnl_mutex); lock(misc_mtx); Then on deadlock scenario: CPU0 waits for rtnl_mutex to unlock, keep rfkill_global_mutex locked CPU1 waits for rfkill_global_mutex to unlock, keep misc_mtx locked CPU2 waits for misc_mtx to unlock, keep rtnl_mutex locked. This dependency can be broken by moving b43_rng_init() outside from rtnl_mutex scope, like on below patch. IIUC b43 random number generator works only if we already started network connection, but this should not be a problem, as b43_rng_read() do not return any data if device is not prepared. You could also remove whole b43 rnd. Everyone know, that HW vendors are influenced by NSA and they random generators do not provide truly random numbers (just kidding ;-) Stanislaw diff --git a/drivers/net/wireless/b43/main.c b/drivers/net/wireless/b43/main.c index ccd24f0a..2c153f9 100644 --- a/drivers/net/wireless/b43/main.c +++ b/drivers/net/wireless/b43/main.c @@ -2475,6 +2475,10 @@ start_ieee80211: goto err_one_core_detach; wl->hw_registred = true; b43_leds_register(wl->current_dev); + + /* Register HW RNG driver */ + b43_rng_init(wl); + goto out; err_one_core_detach: @@ -4636,9 +4640,6 @@ static void b43_wireless_core_exit(struct b43_wldev *dev) if (!dev || b43_status(dev) != B43_STAT_INITIALIZED) return; - /* Unregister HW RNG driver */ - b43_rng_exit(dev->wl); - b43_set_status(dev, B43_STAT_UNINIT); /* Stop the microcode PSM. */ @@ -4795,9 +4796,6 @@ static int b43_wireless_core_init(struct b43_wldev *dev) b43_set_status(dev, B43_STAT_INITIALIZED); - /* Register HW RNG driver */ - b43_rng_init(dev->wl); - out: return err; @@ -5464,6 +5462,9 @@ static void b43_bcma_remove(struct bcma_device *core) b43_one_core_detach(wldev->dev); + /* Unregister HW RNG driver */ + b43_rng_exit(wl); + b43_leds_unregister(wl); ieee80211_free_hw(wl->hw); -- 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
