On Monday 25 May 2009, Eric Dumazet wrote: > Rafael J. Wysocki a écrit : > > This message has been generated automatically as a part of a report > > of recent regressions. > > > > The following bug entry is on the current list of known regressions > > from 2.6.29. Please verify if it still should be listed and let me know > > (either way). > > > > > > Bug-Entry : http://bugzilla.kernel.org/show_bug.cgi?id=13339 > > Subject : rtable leak in ipv4/route.c > > Submitter : Alexander V. Lukyanov <lav@xxxxxx> > > Date : 2009-05-18 14:10 (7 days old) > > > > Bug was present in 2.6.29, so its a regression from 2.6.28 > > It is solved and available in David tree (net-2.6), and scheduled for stable submission > > commit 1ddbcb005c395518c2cd0df504cff3d4b5c85853 > net: fix rtable leak in net/ipv4/route.c > > Alexander V. Lukyanov found a regression in 2.6.29 and made a complete > analysis found in http://bugzilla.kernel.org/show_bug.cgi?id=13339 > Quoted here because its a perfect one : > > begin_of_quotation > 2.6.29 patch has introduced flexible route cache rebuilding. Unfortunately the > patch has at least one critical flaw, and another problem. > > rt_intern_hash calculates rthi pointer, which is later used for new entry > insertion. The same loop calculates cand pointer which is used to clean the > list. If the pointers are the same, rtable leak occurs, as first the cand is > removed then the new entry is appended to it. > > This leak leads to unregister_netdevice problem (usage count > 0). > > Another problem of the patch is that it tries to insert the entries in certain > order, to facilitate counting of entries distinct by all but QoS parameters. > Unfortunately, referencing an existing rtable entry moves it to list beginning, > to speed up further lookups, so the carefully built order is destroyed. > > For the first problem the simplest patch it to set rthi=0 when rthi==cand, but > it will also destroy the ordering. > end_of_quotation > > Problematic commit is 1080d709fb9d8cd4392f93476ee46a9d6ea05a5b > (net: implement emergency route cache rebulds when gc_elasticity is exceeded) > > Trying to keep dst_entries ordered is too complex and breaks the fact that > order should depend on the frequency of use for garbage collection. > > A possible fix is to make rt_intern_hash() simpler, and only makes > rt_check_expire() a litle bit smarter, being able to cope with an arbitrary > entries order. The added loop is running on cache hot data, while cpu > is prefetching next object, so should be unnoticied. > > Reported-and-analyzed-by: Alexander V. Lukyanov <lav@xxxxxx> > Signed-off-by: Eric Dumazet <dada1@xxxxxxxxxxxxx> > Acked-by: Neil Horman <nhorman@xxxxxxxxxxxxx> > Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx> Thanks, updated. Rafael -- To unsubscribe from this list: send the line "unsubscribe kernel-testers" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
