On Fri, 2019-09-27 at 11:41 -0400, Aaron Hill wrote: > The mac80211 subsystem maintains per-cpu stat counters for receive and > transmit operations. Previously, preemption was not disabled when > updating these counters. This creates a race condition where two cpus > could attempt to update the same counters using non-atomic operations. > > This was causing a > 'BUG: using smp_processor_id() in preemptible [00000000] code' > message to be printed, along with a stacktrace. This was reported > in a few different places: > > * https://www.spinics.net/lists/linux-wireless/msg189992.html > * https://bugzilla.kernel.org/show_bug.cgi?id=204127 > > This patch adds calls to preempt_disable() and preempt_enable() > surrounding the updating of the stat counters. That seems like basically the same as what Jiri reported, but now I'm even more confused... Ah. CONFIG_PREEMPT_RCU... But if we keep BHs disabled, it should still be OK, so what I suggested to Jiri will also address this I think? diff --git a/net/mac80211/util.c b/net/mac80211/util.c index 051a02ddcb85..ad1e88958da2 100644 --- a/net/mac80211/util.c +++ b/net/mac80211/util.c @@ -273,9 +273,9 @@ static void __ieee80211_wake_txqs(struct ieee80211_sub_if_data *sdata, int ac) &txqi->flags)) continue; - spin_unlock_bh(&fq->lock); + spin_unlock(&fq->lock); drv_wake_tx_queue(local, txqi); - spin_lock_bh(&fq->lock); + spin_lock(&fq->lock); } } johannes
