On Fri, Oct 6, 2017 at 8:21 AM, Paolo Abeni <pab...@redhat.com> wrote: > Hi, > > On Fri, 2017-10-06 at 07:37 -0700, Eric Dumazet wrote: >> On Fri, 2017-10-06 at 14:57 +0200, Paolo Abeni wrote: >> > Enabling CONFIG_RCU_NOREF_DEBUG gives the following splat when >> > processing tcp packets: >> > >> > to-be-untracked noref entity ffff942cb71ea300 not found in cache >> > ------------[ cut here ]------------ >> > WARNING: CPU: 24 PID: 178 at kernel/rcu/noref_debug.c:54 >> > rcu_track_noref+0xa4/0xf0 >> > Modules linked in: intel_rapl sb_edac x86_pkg_temp_thermal >> > intel_powerclamp coretemp kvm_intel kvm irqbypass crct10dif_pclmul >> > crc32_pclmul ghash_clmulni_intel pcbc aesni_intel crypto_simd glue_helper >> > cryptd iTCO_wdt ipmi_ssif mei_me iTCO_vendor_support mei dcdbas lpc_ich >> > ipmi_si mxm_wmi sg pcspkr ipmi_devintf ipmi_msghandler acpi_power_meter >> > shpchp wmi nfsd auth_rpcgss nfs_acl lockd grace sunrpc ip_tables xfs >> > libcrc32c sd_mod mgag200 drm_kms_helper syscopyarea sysfillrect sysimgblt >> > fb_sys_fops ttm igb drm ixgbe mdio crc32c_intel ahci ptp i2c_algo_bit >> > libahci pps_core i2c_core libata dca dm_mirror dm_region_hash dm_log dm_mod >> > CPU: 24 PID: 178 Comm: ksoftirqd/24 Not tainted >> > 4.14.0-rc1.noref_route+ #1610 >> > Hardware name: Dell Inc. PowerEdge R730/072T6D, BIOS 2.4.3 >> > 01/17/2017 >> > task: ffff940e48300000 task.stack: ffffaec406a20000 >> > RIP: 0010:rcu_track_noref+0xa4/0xf0 >> > RSP: 0018:ffffaec406a238e0 EFLAGS: 00010246 >> > RAX: 0000000000000040 RBX: 0000000000000000 RCX: >> > 0000000000000002 >> > RDX: 0000000000000000 RSI: 0000000000000000 RDI: >> > 0000000000000292 >> > RBP: ffffaec406a238e0 R08: 0000000000000000 R09: >> > 0000000000000000
> Thank you for the feedback. > > I most probably messed-up while extracting the info from dmsg, as this > issue gives a couple of splats almost concurrently. Please let me re-do > the test and post a more resonable dmsg. > > The problem with the current code is that in the tcp_rcv_established() > -> tcp_queue_rcv() path, the skb_dst() is not cleared. > In any case, I would rather put one skb_dst_drop() right after the last possible use of skb dst in TCP stack, probably after sk_rx_dst_set() call. Trying to move it in multiple places has been error prone, even if current code is not buggy.
