Subject: Instable kernel (2.6.29 or 2.6.31) on MPC8548 with 2 GByte RAM

From: willy jacobs <[email-masked]>
Date: Thu, 15 Oct 2009 12:13:40 +0200

On our MPC8548 (latest die revision) based boards with 2 GByte DDR2 RAM we see an stable kernel when

CONFIG_HIGHMEM is not set

In this case only the first 768 MB will be used (as reported by /proc/cpuinfo).
Tested with/without the RT-patches for 2.6.29.6(-rt23) and 2.6.31.2(-rt13) kernels.

With CONFIG_HIGHMEM=y (2048 MB reported) we see (under "heavy" load conditions) regulary page
errors like this (with/without RT patches):

BUG: Bad page state in process loadgen  pfn:7e31d
page:c17c23a0 flags:80000000 count:0 mapcount:-128 mapping:(null) index:48105
Call Trace:
[ef867d20] [c00072ac] show_stack+0x34/0x160 (unreliable)
[ef867d50] [c006fcd0] bad_page+0x90/0x13c
[ef867d70] [c0070d94] get_page_from_freelist+0x424/0x45c
[ef867de0] [c0070ea4] __alloc_pages_nodemask+0xd8/0x48c
[ef867e40] [c0082bf0] handle_mm_fault+0x404/0x740
[ef867e90] [c00131bc] do_page_fault+0x150/0x460
[ef867f40] [c001017c] handle_page_fault+0xc/0x80

With the RT-patches we see already during Linux startup at lot of these errors (from several processes):

BUG: scheduling while atomic: pam_console_app/0x00000001/802, CPU#0
Modules linked in:
Call Trace:
[ef28dce0] [c00072ac] show_stack+0x34/0x160 (unreliable)
[ef28dd10] [c002fa90] __schedule_bug+0x6c/0x80
[ef28dd30] [c02660fc] __schedule+0x264/0x338
[ef28dd60] [c0266400] schedule+0x1c/0x40
[ef28dd70] [c0267898] rt_spin_lock_slowlock+0x124/0x264
[ef28dde0] [c0079154] __lru_cache_add+0x24/0xa8
[ef28de00] [c008ee04] page_add_new_anon_rmap+0x58/0x88
[ef28de20] [c0086ff8] handle_mm_fault+0x5a4/0x804
[ef28de80] [c0013590] do_page_fault+0x14c/0x49c
[ef28df40] [c00101c4] handle_page_fault+0xc/0x80
BUG: scheduling while atomic: pam_console_app/0x00000001/807, CPU#0
Modules linked in:
Call Trace:
[ef323a30] [c00072ac] show_stack+0x34/0x160 (unreliable)
[ef323a60] [c002fa90] __schedule_bug+0x6c/0x80
[ef323a80] [c02660fc] __schedule+0x264/0x338
[ef323ab0] [c0266400] schedule+0x1c/0x40
[ef323ac0] [c0267898] rt_spin_lock_slowlock+0x124/0x264
[ef323b30] [c0079154] __lru_cache_add+0x24/0xa8
[ef323b50] [c008ee04] page_add_new_anon_rmap+0x58/0x88
[ef323b70] [c0086ff8] handle_mm_fault+0x5a4/0x804
[ef323bd0] [c0013590] do_page_fault+0x14c/0x49c
[ef323c90] [c00101c4] handle_page_fault+0xc/0x80
[ef323d50] [00000007] 0x7
[ef323d80] [c0071320] generic_file_aio_read+0x2d4/0x6bc
[ef323e00] [c00ffe98] nfs_file_read+0x124/0x178
[ef323e30] [c009d56c] do_sync_read+0xc4/0x138
[ef323ef0] [c009e0a4] vfs_read+0xc4/0x188
[ef323f10] [c009e514] sys_read+0x4c/0x90
[ef323f40] [c000fd84] ret_from_syscall+0x0/0x3c

Anyone experience with MPC8548 with 2 GByte RAM (HIGHMEM)?

Regards,
-- 
willy
Unclassified

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