On Tue, Apr 02, 2013 at 11:16:26AM -0700, Bing Zhao wrote: > Hi Andi, > > [...] > > > + spin_lock_irqsave(&priv_tmp->wmm.ra_list_spinlock, flags); > > + BUG_ON(atomic_read(&priv_tmp->wmm.tx_pkts_queued)); > > + spin_unlock_irqrestore(&priv_tmp->wmm.ra_list_spinlock, flags); > > + > > /* No packet at any TID for this priv. Mark as such > > * to skip checking TIDs for this priv (until pkt is > > * added). > > atomic_set(hqp, NO_PKT_PRIO_TID); > > > > > > Which crashed. Hence searching for queued packets and adding new ones is > > not synchronized, new packets can be added while searching the WMM > > queues. If a packet is added right before setting max prio to NO_PKT, > > that packet is trapped and creates an infinite loop. > > > > Because of the new packet tx_pkts_queued is at least 1, indicating wmm > > lists are not empty. Opposing that max prio is NO_PKT, which means "skip > > this wmm queue, it has no packets". > > The infinite loop results, because the main loop checks the wmm lists > > for not empty (tx_pkts_queued != 0), but then finds no packet since it > > skips the wmm queue where it is located on. This will never end, unless > > a new packet is added which will restore max prio. > > Thanks for your analysis. > > > One possible solution is is to rely on tx_pkts_queued solely for > > checking wmm queue to be empty, and drop the NO_PKT define. > > FYI, Yogesh suggested another fix (attached). Started with similar patch, but then learned that NO_PKT_PRIO_TID is not needed at all. It only adds complexity, rely on tx_pkts_queued! On top, bss_prio_tbl should be locked as well. > > [...] > > > seems to be intruduced with this patch: > > 17e8cec 05-16-2011 mwifiex: CPU mips optimization with NO_PKT_PRIO_TID > > > > I was wondering why hasn't happened more frequently. Evtl. if the > > interface is working in bridge mode, new packets might be added to the > > WMM queue with the trapped packet. 2c > > > > I prepared a few patches, fixing above bug as suggested and plus some > > cleanup patches I did while trying to get an understanding. Pls review. > > Thanks for the patches. We will review them and run some WMM tests. Thanks, looking forward to that. Andi -- 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
