On Thu, 2015-04-23 at 21:46 +0100, Thomas Graf wrote: > On 04/23/15 at 04:38pm, Johannes Berg wrote: > > From: Johannes Berg <johannes.b...@intel.com> > > > > The conversion of mac80211's station table to rhashtable had a bug > > that I found by accident in code review, that hadn't been found as > > rhashtable apparently managed to have a maximum hash chain length > > of one (!) in all our testing. > > This is the desired chain length ;-)
Sure. But I had a bug in my handling of collisions, so I explicitly wanted to test them. After all, they are in some ways expected in a hash table :) > > At that point, rhashtable WARNed in rhashtable_insert_rehash() but > > didn't actually reject the hash table insertion. This caused it to > > lose insertions - my master list of stations would have 9 entries, > > but the rhashtable only had 5. This may warrant a deeper look, but > > that WARN_ON() just shouldn't happen. > > The warning got fixed recently (51bb8e331b) and > rhashtable_insert_rehash() now only allows a single rehash if at > max_size already. It will now return -EBUSY. > > Insertions may still fail while the table is above 100% utilization > so this fix is absolutely needed though. Yeah just failing would be a bit strange. > > Fix this by not returning true from rht_grow_above_100() when the > > rhashtable's max_size has been reached - in this case the user is > > explicitly configuring it to be at most that big, so even if it's > > now above 100% it shouldn't attempt to resize. > > Good catch. I wonder whether we want to trigger a periodic rehash > in an interval in this situation or just leave this up to the user > to setup a timer himself. You could just document it that it's probably useful if max_size is set? I'm just going to be setting max_size for debug purposes, so don't really care all that much. johannes -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
