regression for cris architecture

[Waldemar Brodkorb]

Hi,

I am regulary running some tests with qemu-system-cris, but getting following
stacktraces on boot now (with 4.8.6, 4.7.9 worked fine):

[    7.260691] Unable to handle kernel NULL pointer dereference
[    7.260919] Linux 4.8.6-1 #4 Sun Nov 6 17:48:18 CET 2016
[    7.260955] Oops: 0000
[    7.260999] CPU: 0  
[    7.261064] ERP: c0024b82 SRP: c0024b7a  CCS: 0e00a008 USP: af9dfd24 MOF: e79a1af9
[    7.261110]  r0: 00000000  r1: 00000000   r2: c020091a  r3: c004da14
[    7.261161]  r4: c0084714  r5: c04522b4   r6: c00441f2  r7: c004351a
[    7.261214]  r8: c00435c2  r9: c1e5fdc0  r10: c1e5fdbc r11: 00000000
[    7.261265] r12: c00b6ee0 r13: c1e5fdc4 oR10: c1e5fdbc acr: c1e5fdc0
[    7.261286]  sp: c1e5fd50
[    7.261311]        Data MMU Cause: 00000117
[    7.261334] Instruction MMU Cause: 3aaca017
[    7.261379] Process mkdir (pid: 26, stackpage=c1f0f440)
[    7.261439]
[    7.261439] Stack from af9dfd24:
[    7.261439]
[    7.261516] 00000004 00000012
[    7.261567] 00000001 00000000
[    7.261591] 00000000 00000001
[    7.261615] 000041ed 00000010
[    7.261644]
[    7.261644]        00000000
[    7.261683] 00000000 00000000
[    7.261707] 00000000 00000000
[    7.261729] 00000000 00000000
[    7.261754] 00002000
[    7.261762]
[    7.261774] 00000000 00000000
[    7.261797] 00000000 08583b00
[    7.261822] 00000002 3ab1bbe0
[    7.261850] 3ab0c238 3aac93b2
[    7.261895]
[    7.261895] Call Trace:
[    7.262003] Stack from c1e5fc54:
[    7.262003]
[    7.262021] c1e5fd50 c00047b8
[    7.262049] af9dfd24 c1e5fd9c
[    7.262077] 3aaca017 c000553e
[    7.262105] c1e5fdc0 e79a1af9
[    7.262128]
[    7.262128]        c0042a70
[    7.262155] c01c00c4 00000000
[    7.262181] c1e5fd50 c1e401b4
[    7.262208] c00048da 00000000
[    7.262233] c1e5fd50
[    7.262241]
[    7.262256] c1f0f440 00000000
[    7.262281] c0004f9c 00c02008
[    7.262306] 00000000 00000000
[    7.262331] c020091a c004da14
[    7.262355]
[    7.262355] Call Trace: [<c00047b8>] show_stack+0x0/0x8c
[    7.263279] [<c000553e>] show_registers+0x14e/0x1c6
[    7.263314] [<c0042a70>] printk+0x0/0x2c
[    7.263345] [<c00048da>] die_if_kernel+0x6c/0x96
[    7.263383] [<c0004f9c>] do_page_fault+0x2c6/0x34a
[    7.263417] [<c004da14>] __put_page+0x0/0x40
[    7.263464] [<c0084714>] simple_readpage+0x0/0x72
[    7.263500] [<c00441f2>] pagecache_get_page+0x0/0x1c6
[    7.263532] [<c004351a>] unlock_page+0x0/0x3c
[    7.263563] [<c00435c2>] __lock_page+0x0/0x74
[    7.263598] [<c01632a2>] down_read+0x0/0x12
[    7.263635] [<c005e89e>] find_vma+0x12/0x54
[    7.263665] [<c0025340>] up_read+0xc/0x12
[    7.263696] [<c0004e9a>] do_page_fault+0x1c4/0x34a
[    7.263731] [<c00081aa>] d_mmu_refill+0x10a/0x112
[    7.263761] [<c004da14>] __put_page+0x0/0x40
[    7.263793] [<c0084714>] simple_readpage+0x0/0x72
[    7.263827] [<c00441f2>] pagecache_get_page+0x0/0x1c6
[    7.263859] [<c004351a>] unlock_page+0x0/0x3c
[    7.263890] [<c00435c2>] __lock_page+0x0/0x74
[    7.263925] [<c00b6ee0>] memset+0xf6/0x138
[    7.263961] [<c0024b7a>] __wake_up_bit+0x1c/0x44
[    7.263996] [<c0024b82>] __wake_up_bit+0x24/0x44
[    7.264029] [<c004354e>] unlock_page+0x34/0x3c
[    7.264060] [<c008477e>] simple_readpage+0x6a/0x72
[    7.264095] [<c00444a0>] do_read_cache_page+0xaa/0x252
[    7.264125] [<c0071652>] page_get_link+0x0/0xcc
[    7.264154] [<c007105a>] path_put+0x0/0x24
[    7.264187] [<c0044660>] read_cache_page+0x18/0x20
[    7.264218] [<c00716d2>] page_get_link+0x80/0xcc
[    7.264250] [<c0072df2>] trailing_symlink+0x12a/0x184
[    7.264281] [<c007389c>] link_path_walk+0x0/0x358
[    7.264311] [<c0073cd0>] path_lookupat+0x84/0xe8
[    7.264341] [<c0073c4c>] path_lookupat+0x0/0xe8
[    7.264372] [<c0074362>] user_path_at_empty+0x0/0x3e
[    7.264404] [<c006d516>] vfs_getattr_nosec+0x0/0x32
[    7.264436] [<c00742a4>] filename_lookup+0x5c/0xa6
[    7.264469] [<c0074028>] getname_flags+0x22/0x170
[    7.264500] [<c0074394>] user_path_at_empty+0x32/0x3e
[    7.264533] [<c006d688>] vfs_fstatat+0x4a/0x88
[    7.264566] [<c006d6da>] vfs_stat+0x14/0x1a
[    7.264630] [<c006dda6>] SyS_stat64+0x16/0x32
[    7.264662] [<c007445c>] filename_create+0x0/0xf4
[    7.264694] [<c0075946>] SyS_mkdirat+0x3e/0xa6
[    7.264725] [<c00759c2>] SyS_mkdir+0x14/0x1a
[    7.264756] [<c000523a>] _syscall_traced+0x22/0x2a
[    7.264773]
[    7.264773] Code: 09 00 2e a6 0c e1 ef 2b 10 e1 ef 1b (60) fa ef 06 12 30 4c d2 2e d6 41 c2
[    7.265174] ---[ end trace 7fbf74436dc80fa8 ]---
..


I bisected it and the error occurs since commit:
commit 599d0c954f91d0689c9bb421b5bc04ea02437a41
Author: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Date:   Thu Jul 28 15:45:31 2016 -0700

    mm, vmscan: move LRU lists to node

Any idea how to fix this?

best regards
 Waldemar