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 ;-) > In order to test the bug and verify the fix I set my rhashtable's > max_size very low (4) in order to force getting hash collisions. > > 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. > 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. > This fixes the "lost insertion" issue and consequently allows my > code to display its error (and verify my fix for it.) > > Signed-off-by: Johannes Berg <johannes.b...@intel.com> Acked-by: Thomas Graf <tg...@suug.ch> -- 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
