arm: lockdep complaining about static memory allocations

Sat Nov 21 08:09:59 EST 2020

Jan Kardell skrev:
> Hi,
>
> I'm lifting our old barrier_braker code on an omap am3552 custom 
> board, and building it on master per 13 november. I currently run it 
> as an zImage-initramfs, but the board normally uses ubifs on nand 
> flash. I get exceptions logged to dmesg, included snippets from the 
> logs  as attachment. I also saw it with an older kernel, 5.4.68 from 
> september. I'm not sure how to debug this and would be happy if 
> someone can point me in the right direction. It looks to me it is 
> something wrong with allocating/freeing net devices in the kernel. 
> Maybe there are OpenWrt patches affecting this?
>
> Regards
> //Jan

Turns out this is not an OpenWrt thing. After enabling CONFIG_PREEMT i 
started to see allocation of net devices in the memory that previously 
was initmem, and lockdep detect that as static memory. To linux 5.2 a 
patch for s390 in commit 7a5da02de8d6eafba99556f8c98e5313edebb449 added 
the function arch_is_kernel_initmem_freed(). It has later been added for 
powerpc and x86 too. I now believe that is needed for arm as well. 
Though I don't know the inner workings of memory management so I don't 
know if an identical solution as s390 and powerpc will do for arm. The 
commit message for s390 says "virt == phys", but that seems not to be 
the case for my arm system.

I did a "dummy" arch_is_kernel_initmem_freed() with a printk to verify 
that the address is in the initmem area:

|[ 73.966965] Address 0xc0e6e630 is in initmem! [ 73.978934] 
------------[ cut here ]------------ [ 74.001003] WARNING: CPU: 0 PID: 
2008 at kernel/locking/lockdep.c:1119 alloc_netdev_mqs+0xb4/0x3b0|

This also makes me wonder if more archs needs this and maybe a more 
general solution, but that's definitely out of my league...

//Jan

-- 

"I have always wished for my computer to be as easy to use as my telephone; my wish has come true because I can no longer figure out how to use my telephone."
- Bjarne Stroustrup

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[   92.168789] ------------[ cut here ]------------
[   92.198989] WARNING: CPU: 0 PID: 2015 at kernel/locking/lockdep.c:1119 alloc_netdev_mqs+0xb4/0x3b0
[   92.230384] Modules linked in: pppoe ppp_async option usb_wwan pppox ppp_generic pl2303 ipt_REJECT ftdi_sio cp210x xt_time xt_tcpudp xt_state xt_recent xt_policy xt_nat xt_multiport xt_mark xt_mac xt_limit xt_helper xt_esp xt_conntrack xt_connmark xt_connlimit xt_connbytes xt_comment xt_TCPMSS xt_REDIRECT xt_MASQUERADE xt_LOG usbserial slhc nf_reject_ipv4 nf_log_ipv4 nf_flow_table_hw nf_flow_table nf_conntrack_rtcache nf_conntrack_netlink nf_conncount iptable_nat iptable_mangle iptable_filter ipt_ah ip_tables cdc_acm tps65217_poweroff xt_set ip_set_list_set ip_set_hash_netportnet ip_set_hash_netport ip_set_hash_netnet ip_set_hash_netiface ip_set_hash_net ip_set_hash_mac ip_set_hash_ipportnet ip_set_hash_ipportip ip_set_hash_ipport ip_set_hash_ipmark ip_set_hash_ip ip_set_bitmap_port ip_set_bitmap_ipmac ip_set_bitmap_ip ip_set nfnetlink ip6table_nat nf_nat nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 ip6t_NPT nf_log_ipv6 nf_log_common ip6table_mangle ip6table_filter ip6_tables ip6t_REJECT
[   92.230683]  x_tables nf_reject_ipv6 ipip tunnel4 ip_tunnel nls_utf8 nls_iso8859_15 ecdh_generic ecc crypto_user algif_skcipher algif_rng algif_hash algif_aead af_alg kpp cmac arc4 usb_storage mii
[   92.559823] CPU: 0 PID: 2015 Comm: netifd Not tainted 5.4.75 #0
[   92.566083] Hardware name: Generic AM33XX (Flattened Device Tree)
[   92.572538] [<c010e654>] (unwind_backtrace) from [<c010b3d8>] (show_stack+0x10/0x14)
[   92.580705] [<c010b3d8>] (show_stack) from [<c077fb50>] (dump_stack+0x94/0xa8)
[   92.588324] [<c077fb50>] (dump_stack) from [<c0129410>] (__warn+0xbc/0xd8)
[   92.595564] [<c0129410>] (__warn) from [<c012947c>] (warn_slowpath_fmt+0x50/0x94)
[   92.603456] [<c012947c>] (warn_slowpath_fmt) from [<c060de64>] (alloc_netdev_mqs+0xb4/0x3b0)
[   92.612357] [<c060de64>] (alloc_netdev_mqs) from [<c073ba04>] (br_add_bridge+0x28/0x70)
[   92.620783] [<c073ba04>] (br_add_bridge) from [<c073d944>] (br_ioctl_deviceless_stub+0x20c/0x408)
[   92.630122] [<c073d944>] (br_ioctl_deviceless_stub) from [<c05f0dd4>] (sock_ioctl+0x248/0x5ac)
[   92.639184] [<c05f0dd4>] (sock_ioctl) from [<c023d7dc>] (do_vfs_ioctl+0xa0/0x918)
[   92.647060] [<c023d7dc>] (do_vfs_ioctl) from [<c023e0b0>] (ksys_ioctl+0x5c/0x80)
[   92.654843] [<c023e0b0>] (ksys_ioctl) from [<c0101000>] (ret_fast_syscall+0x0/0x54)
[   92.662894] Exception stack(0xc0e81fa8 to 0xc0e81ff0)
[   92.668216] 1fa0:                   b6f01280 b6f012e0 00000008 000089a0 b6f012e0 be992a10
[   92.676821] 1fc0: b6f01280 b6f012e0 b6f4af20 00000036 be992b38 b6f4adb0 0002e68f b6f4af44
[   92.685422] 1fe0: 0003fd2c be9929f8 0001e778 b6fa8844
[   92.845970] ---[ end trace af697b21708fc24a ]---

[  806.192698] ------------[ cut here ]------------
[  806.197644] WARNING: CPU: 0 PID: 2606 at kernel/locking/lockdep.c:5188 free_netdev+0xa8/0x108
[  806.241216] Modules linked in: pppoe ppp_async option usb_wwan pppox ppp_generic pl2303 ipt_REJECT ftdi_sio cp210x xt_time xt_tcpudp xt_state xt_recent xt_policy xt_nat xt_multiport xt_mark xt_mac xt_limit xt_helper xt_esp xt_conntrack xt_connmark xt_connlimit xt_connbytes xt_comment xt_TCPMSS xt_REDIRECT xt_MASQUERADE xt_LOG usbserial slhc nf_reject_ipv4 nf_log_ipv4 nf_flow_table_hw nf_flow_table nf_conntrack_rtcache nf_conntrack_netlink nf_conncount iptable_nat iptable_mangle iptable_filter ipt_ah ip_tables cdc_acm tps65217_poweroff xt_set ip_set_list_set ip_set_hash_netportnet ip_set_hash_netport ip_set_hash_netnet ip_set_hash_netiface ip_set_hash_net ip_set_hash_mac ip_set_hash_ipportnet ip_set_hash_ipportip ip_set_hash_ipport ip_set_hash_ipmark ip_set_hash_ip ip_set_bitmap_port ip_set_bitmap_ipmac ip_set_bitmap_ip ip_set nfnetlink ip6table_nat nf_nat nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 ip6t_NPT nf_log_ipv6 nf_log_common ip6table_mangle ip6table_filter ip6_tables ip6t_REJECT
[  806.241846]  x_tables nf_reject_ipv6 ipip tunnel4 ip_tunnel nls_utf8 nls_iso8859_15 ecdh_generic ecc crypto_user algif_skcipher algif_rng algif_hash algif_aead af_alg kpp cmac arc4 usb_storage mii
[  806.483041] CPU: 0 PID: 2606 Comm: pppd Tainted: G        W         5.4.75 #0
[  806.490574] Hardware name: Generic AM33XX (Flattened Device Tree)
[  806.497033] [<c010e654>] (unwind_backtrace) from [<c010b3d8>] (show_stack+0x10/0x14)
[  806.505196] [<c010b3d8>] (show_stack) from [<c077fb50>] (dump_stack+0x94/0xa8)
[  806.512815] [<c077fb50>] (dump_stack) from [<c0129410>] (__warn+0xbc/0xd8)
[  806.520053] [<c0129410>] (__warn) from [<c012947c>] (warn_slowpath_fmt+0x50/0x94)
[  806.527942] [<c012947c>] (warn_slowpath_fmt) from [<c060cde8>] (free_netdev+0xa8/0x108)
[  806.536406] [<c060cde8>] (free_netdev) from [<bf293de8>] (ppp_release+0x84/0x9c [ppp_generic])
[  806.545575] [<bf293de8>] (ppp_release [ppp_generic]) from [<c022b59c>] (__fput+0x88/0x220)
[  806.554295] [<c022b59c>] (__fput) from [<c0146cac>] (task_work_run+0x8c/0xa8)
[  806.561810] [<c0146cac>] (task_work_run) from [<c010a710>] (do_work_pending+0xa0/0x528)
[  806.570233] [<c010a710>] (do_work_pending) from [<c010106c>] (slow_work_pending+0xc/0x20)
[  806.578830] Exception stack(0xc3039fb0 to 0xc3039ff8)
[  806.584150] 9fa0:                                     00000000 00000000 00000000 00000000
[  806.592754] 9fc0: 00000000 00000000 004d0040 00000006 004d3730 00000004 004e1994 00000000
[  806.601356] 9fe0: bea26ac8 bea26ab8 b6f45538 b6f449f8 60000010 0000000f
[  806.775231] ---[ end trace af697b21708fc24b ]---