On 06/20/2017 08:03 PM, David Ahern wrote:
On 6/20/17 5:41 PM, Ben Greear wrote:
On 06/20/2017 11:05 AM, Michal Kubecek wrote:
On Tue, Jun 20, 2017 at 07:12:27AM -0700, Ben Greear wrote:
On 06/14/2017 03:25 PM, David Ahern wrote:
On 6/14/17 4:23 PM, Ben Greear wrote:
On 06/13/2017 07:27 PM, David Ahern wrote:
Let's try a targeted debug patch. See attached
I had to change it to pr_err so it would go to our serial console
since the system locked hard on crash,
and that appears to be enough to change the timing where we can no
longer
reproduce the problem.
ok, let's figure out which one is doing that. There are 3 debug
statements. I suspect fib6_del_route is the one setting the state to
FWS_U. Can you remove the debug prints in fib6_repair_tree and
fib6_walk_continue and try again?
We cannot reproduce with just that one printf in the kernel either. It
must change the timing too much to trigger the bug.
You might try trace_printk() which should have less impact (don't forget
to enable /proc/sys/kernel/ftrace_dump_on_oops).
We cannot reproduce with trace_printk() either.
I think that suggests the walker state is set to FWS_U in
fib6_del_route, and it is the FWS_U case in fib6_walk_continue that
triggers the fault -- the null parent (pn = fn->parent). So we have the
2 areas of code that are interacting.
I'm on a road trip through the end of this week with little time to
focus on this problem. I'll get back to you another suggestion when I can.
So, though I don't know the right way to fix it, the patch below appears
to make the system not crash.
diff --git a/net/ipv6/ip6_fib.c b/net/ipv6/ip6_fib.c
index 68b9cc7..bf19a14 100644
--- a/net/ipv6/ip6_fib.c
+++ b/net/ipv6/ip6_fib.c
@@ -1614,6 +1614,12 @@ static int fib6_walk_continue(struct fib6_walker *w)
pn = fn->parent;
w->node = pn;
#ifdef CONFIG_IPV6_SUBTREES
+ if (WARN_ON_ONCE(!pn)) {
+ pr_err("FWS-U, w: %p fn: %p pn: %p\n",
+ w, fn, pn);
+ /* Attempt to work around crash that has been
here forever. --Ben */
+ return 0;
+ }
if (FIB6_SUBTREE(pn) == fn) {
WARN_ON(!(fn->fn_flags & RTN_ROOT));
w->state = FWS_L;
The printout looks like this (when adding 4000 mac-vlans, so it is pretty
rare). PN is definitely NULL sometimes:
[root@2u-6n ~]# journalctl -f|grep FWS
Jan 24 15:48:05 2u-6n kernel: IPv6: FWS-U, w: ffff8807ea121ba0 fn:
ffff880856a09260 pn: (null)
Jan 24 15:51:15 2u-6n kernel: IPv6: FWS-U, w: ffff8807e3963de0 fn:
ffff880856a09260 pn: (null)
Jan 24 15:51:15 2u-6n kernel: IPv6: FWS-U, w: ffff88081ac22de0 fn:
ffff880856a09260 pn: (null)
Jan 24 15:53:13 2u-6n kernel: IPv6: FWS-U, w: ffff8808290c69c0 fn:
ffff8807e369f920 pn: (null)
Jan 24 15:53:24 2u-6n kernel: IPv6: FWS-U, w: ffff8807ea3156c0 fn:
ffff88082d1eeb60 pn: (null)
8066 Jan 24 15:48:04 2u-6n kernel: 8021q: adding VLAN 0 to HW filter on device
eth2#1006
8067 Jan 24 15:48:05 2u-6n kernel: ------------[ cut here ]------------
8068 Jan 24 15:48:05 2u-6n kernel: WARNING: CPU: 5 PID: 3346 at /home/greearb/git/linux-4.13.dev.y/net/ipv6/ip6_fib.c:1617 fib6_walk_continue+
0x154/0x1b0 [ipv6]
8069 Jan 24 15:48:05 2u-6n kernel: Modules linked in: 8021q garp mrp stp llc fuse macvlan wanlink(O) pktgen ipmi_ssif coretemp intel_rapl sb_edac
x86_pkg_temp_thermal intel_powerclamp kvm_intel kvm ath9k irqbypass iTCO_wdt ath9k_common iTCO_vendor_support ath9k_hw ath i2c_i801 mac80211 joydev
lpc_ich cfg80211 ioatdma shpchp tpm_tis tpm_tis_core wmi tpm ipmi_si ipmi_devintf ipmi_msghandler acpi_pad acpi_power_meter nfsd auth_rpcgss nfs_acl
sch_fq_codel lockd grace sunrpc ast drm_kms_helper ttm drm igb hwmon ptp pps_core dca i2c_algo_bit i2c_core ipv6 crc_ccitt
8070 Jan 24 15:48:05 2u-6n kernel: CPU: 5 PID: 3346 Comm: ip Tainted: G
O 4.13.16+ #22
8071 Jan 24 15:48:05 2u-6n kernel: Hardware name: Iron_Systems,Inc
CS-CAD-2U-A02/X10SRL-F, BIOS 2.0b 05/02/2017
8072 Jan 24 15:48:05 2u-6n kernel: task: ffff8807e9ef1dc0 task.stack:
ffffc9002083c000
8073 Jan 24 15:48:05 2u-6n kernel: RIP: 0010:fib6_walk_continue+0x154/0x1b0
[ipv6]
8074 Jan 24 15:48:05 2u-6n kernel: RSP: 0018:ffffc9002083fbc0 EFLAGS: 00010246
8075 Jan 24 15:48:05 2u-6n kernel: RAX: 0000000000000000 RBX: ffff8807ea121ba0
RCX: 0000000000000000
8076 Jan 24 15:48:05 2u-6n kernel: RDX: ffff880856a09260 RSI: ffffc9002083fc00
RDI: ffffffff81ef2140
8077 Jan 24 15:48:05 2u-6n kernel: RBP: ffffc9002083fbc8 R08: 0000000000000008
R09: ffff8807e36f6b25
8078 Jan 24 15:48:05 2u-6n kernel: R10: ffffc9002083fb70 R11: 0000000000000000
R12: 0000000000000002
8079 Jan 24 15:48:05 2u-6n kernel: R13: 0000000000000002 R14: ffff8807ea121ba0
R15: ffff8807ebcc8d80
8080 Jan 24 15:48:05 2u-6n kernel: FS: 00007f77a5d0f700(0000)
GS:ffff88087fd40000(0000) knlGS:0000000000000000
8081 Jan 24 15:48:05 2u-6n kernel: CS: 0010 DS: 0000 ES: 0000 CR0:
0000000080050033
8082 Jan 24 15:48:05 2u-6n kernel: CR2: 0000000003d56c88 CR3: 00000007f3106000
CR4: 00000000003406e0
8083 Jan 24 15:48:05 2u-6n kernel: DR0: 0000000000000000 DR1: 0000000000000000
DR2: 0000000000000000
8084 Jan 24 15:48:05 2u-6n kernel: DR3: 0000000000000000 DR6: 00000000fffe0ff0
DR7: 0000000000000400
8085 Jan 24 15:48:05 2u-6n kernel: Call Trace:
8086 Jan 24 15:48:05 2u-6n kernel: inet6_dump_fib+0x1ab/0x2a0 [ipv6]
8087 Jan 24 15:48:05 2u-6n kernel: netlink_dump+0x22c/0x2b0
8088 Jan 24 15:48:05 2u-6n kernel: netlink_recvmsg+0x260/0x3f0
8089 Jan 24 15:48:05 2u-6n kernel: sock_recvmsg+0x38/0x40
8090 Jan 24 15:48:05 2u-6n kernel: ___sys_recvmsg+0xe9/0x230
8091 Jan 24 15:48:05 2u-6n kernel: ? alloc_pages_vma+0x83/0x1e0
8092 Jan 24 15:48:05 2u-6n kernel: ? page_add_new_anon_rmap+0x88/0xc0
8093 Jan 24 15:48:05 2u-6n kernel: ?
lru_cache_add_active_or_unevictable+0x31/0xb0
8094 Jan 24 15:48:05 2u-6n kernel: ? __handle_mm_fault+0x5e5/0xfa0
8095 Jan 24 15:48:05 2u-6n kernel: __sys_recvmsg+0x3d/0x70
8096 Jan 24 15:48:05 2u-6n kernel: ? __sys_recvmsg+0x3d/0x70
8097 Jan 24 15:48:05 2u-6n kernel: SyS_recvmsg+0xd/0x20
8098 Jan 24 15:48:05 2u-6n kernel: do_syscall_64+0x56/0xc0
8099 Jan 24 15:48:05 2u-6n kernel: entry_SYSCALL64_slow_path+0x25/0x25
8100 Jan 24 15:48:05 2u-6n kernel: RIP: 0033:0x7f77a5644030
8101 Jan 24 15:48:05 2u-6n kernel: RSP: 002b:00007ffc3e783e68 EFLAGS: 00000246
ORIG_RAX: 000000000000002f
8102 Jan 24 15:48:05 2u-6n kernel: RAX: ffffffffffffffda RBX: 0000000000000000
RCX: 00007f77a5644030
8103 Jan 24 15:48:05 2u-6n kernel: RDX: 0000000000000000 RSI: 00007ffc3e783ed0
RDI: 0000000000000004
8104 Jan 24 15:48:05 2u-6n kernel: RBP: 00007ffc3e787ef4 R08: 0000000000003fe4
R09: 0
8105 Jan 24 15:48:05 2u-6n kernel: R10: 00007ffc3e783f10 R11: 0000000000000246
R12: 000000000064f360
8106 Jan 24 15:48:05 2u-6n kernel: R13: 00007ffc3e787f60 R14: 0000000000003fe4
R15: 0000000000000000
8107 Jan 24 15:48:05 2u-6n kernel: Code: ff 24 c5 a8 e5 04 a0 f6 42 2a 02 74 68 c7 43 28 01 00 00 00 48 89 c2 e9 c7 fe ff ff c7 43 28 02 00 00 00 48 89
c2 e9 b8 fe ff ff <0f> ff 31 c9 48 89 de 48 c7 c7 78 36 05 a0 e8 65 e4 14 e1 31 c0
8108 Jan 24 15:48:05 2u-6n kernel: ---[ end trace 1d1c7028c9dec459 ]---
8109 Jan 24 15:48:05 2u-6n kernel: IPv6: FWS-U, w: ffff8807ea121ba0 fn:
ffff880856a09260 pn: (null)
8110 Jan 24 15:48:05 2u-6n kernel: 8021q: adding VLAN 0 to HW filter on device
eth2#1008
8111 Jan 24 15:48:05 2u-6n kernel: 8021q: adding VLAN 0 to HW filter on device
eth2#1009
....
Thanks,
Ben
--
Ben Greear <gree...@candelatech.com>
Candela Technologies Inc http://www.candelatech.com
