On 16-11-26 10:29 PM, Roi Dayan wrote: > > > On 27/11/2016 06:47, Roi Dayan wrote: >> >> >> On 27/11/2016 02:33, Daniel Borkmann wrote: >>> On 11/26/2016 12:09 PM, Daniel Borkmann wrote: >>>> On 11/26/2016 07:46 AM, Cong Wang wrote: >>>>> On Thu, Nov 24, 2016 at 7:20 AM, Daniel Borkmann >>>>> <dan...@iogearbox.net> wrote: >>> [...] >>>>>> Ok, strange, qdisc_destroy() calls into ops->destroy(), where ingress >>>>>> drops its entire chain via tcf_destroy_chain(), so that will be NULL >>>>>> eventually. The tps are freed by call_rcu() as well as qdisc itself >>>>>> later on via qdisc_rcu_free(), where it frees per-cpu bstats as well. >>>>>> Outstanding readers should either bail out due to if (!cl) or can >>>>>> still >>>>>> process the chain until read section ends, but during that time, >>>>>> cl->q >>>>>> resp. bstats should be good. Do you happen to know what's at address >>>>>> ffff880a68b04028? I was wondering wrt call_rcu() vs call_rcu_bh(), >>>>>> but >>>>>> at least on ingress (netif_receive_skb_internal()) we hold >>>>>> rcu_read_lock() >>>>>> here. The KASAN report is reliably happening at this location, right? >>>>> >>>>> I am confused as well, I don't see how it could be related to my >>>>> patch yet. >>>>> I will take a deep look in the weekend. >> >> >> >> Hi Cong, >> >> When reported the new trace I didn't mean it's related to your patch, >> I just wanted to point it out it exposed something. I should have been >> clear about it. >> >> >>>> >>>> Ok, I'm currently on the run. Got too late yesterday night, but I'll >>>> write what I found in the evening today, not related to ingress though. >>> >>> Just pushed out my analysis to netdev under "[PATCH net] net, sched: >>> respect >>> rcu grace period on cls destruction". My conclusion is that both >>> issues are >>> actually separate, and that one is small enough where we could route >>> it via >>> net actually. Perhaps this at the same time shrinks your "[PATCH >>> net-next] >>> net_sched: move the empty tp check from ->destroy() to ->delete()" to a >>> reasonable size that it's suitable to net as well. Your >>> ->delete()/->destroy() >>> one is definitely needed, too. The tp->root one is independant of >>> ->delete()/ >>> ->destroy() as they are different races and tp->root could also >>> happen when >>> you just destroy the whole tp directly. I think that seems like a >>> good path >>> forward to me. >>> >>> Thanks, >>> Daniel >> >> >> >> Hi Daniel, >> >> As for the tainted kernel. I was in old (week or two) net-next tree >> and only cherry-picked from latest net-next related patches to >> Mellanox HCA, cls_api, cls_flower, devlink. so those are the tainted >> modules. >> I have the issue reproducing in that tree so wanted it to check it >> with Cong's patch instead of latest net-next. >> I'll try running reproducing the issue with your new patch and later >> try latest net-next as well. >> >> Thanks, >> Roi >> > > Hi, > > I tested "[PATCH net] net, sched: respect rcu grace period on cls > destruction" and could not reproduce my original issue.
Hi Roi, Just so I'm 100% clear. No issue with just the above "respect rcu grace period on cls destruction" per above statement. > I rebased "[Patch net-next] net_sched: move the empty tp check from > ->destroy() to ->delete()" over to test it in the same tree and got into > a new trace in fl_delete. In this case did you test with "net_sched: move the empty tp check from ->destroy() to ->delete()" _only_ or did this include both patches when you see the error below. >From my inspection we really need both patches to get correct behavior. Thanks! John > > [35659.012123] BUG: KASAN: wild-memory-access on address 1ffffffff803ca31 > [35659.020042] Write of size 1 by task ovs-vswitchd/20135 > [35659.025878] CPU: 19 PID: 20135 Comm: ovs-vswitchd Tainted: > G O 4.9.0-rc3+ #18 > [35659.035948] Hardware name: HP ProLiant DL380p Gen8, BIOS P70 07/01/2015 > [35659.043730] Call Trace: > [35659.046619] [<ffffffff95b6dc42>] dump_stack+0x63/0x81 > [35659.052456] [<ffffffff955fbbf8>] kasan_report_error+0x408/0x4e0 > [35659.059402] [<ffffffff955fc2e8>] kasan_report+0x58/0x60 > [35659.065428] [<ffffffff952d5e8d>] ? call_rcu_sched+0x1d/0x20 > [35659.072119] [<ffffffffc01e0701>] ? fl_destroy_filter+0x21/0x30 > [cls_flower] > [35659.080217] [<ffffffffc01e1ccf>] ? fl_delete+0x1df/0x2e0 [cls_flower] > [35659.087580] [<ffffffff955fa4ca>] __asan_store1+0x4a/0x50 > [35659.093697] [<ffffffffc01e1ccf>] fl_delete+0x1df/0x2e0 [cls_flower] > [35659.100870] [<ffffffff9653ecba>] tc_ctl_tfilter+0x10da/0x1b90 > > > 0x1d02 is in fl_delete (net/sched/cls_flower.c:805). > 800 struct cls_fl_filter *f = (struct cls_fl_filter *) arg; > 801 > 802 rhashtable_remove_fast(&head->ht, &f->ht_node, > 803 head->ht_params); > 804 __fl_delete(tp, f); > 805 *last = list_empty(&head->filters); > 806 return 0; > 807 } > > > Thanks, > Roi
