Subject: Re: [PATCH V2 2/2] mm/pgtable/debug: Add test validating architecture page table helpers

From: Christophe Leroy <[email-masked]>
Date: Fri, 13 Sep 2019 08:30:25 +0200

Le 12/09/2019 à 17:52, Christophe Leroy a écrit :
> 
> 
> Le 12/09/2019 à 17:36, Christophe Leroy a écrit :
>>
>>
>> Le 12/09/2019 à 17:00, Christophe Leroy a écrit :
>>>
>>>
>>> On 09/12/2019 06:02 AM, Anshuman Khandual wrote:
>>>> This adds a test module which will validate architecture page table 
>>>> helpers
>>>> and accessors regarding compliance with generic MM semantics 
>>>> expectations.
>>>> This will help various architectures in validating changes to the 
>>>> existing
>>>> page table helpers or addition of new ones.
>>>>
>>>> Test page table and memory pages creating it's entries at various 
>>>> level are
>>>> all allocated from system memory with required alignments. If memory 
>>>> pages
>>>> with required size and alignment could not be allocated, then all 
>>>> depending
>>>> individual tests are skipped.
>>>
>>> Build failure on powerpc book3s/32. This is because asm/highmem.h is 
>>> missing. It can't be included from asm/book3s/32/pgtable.h because it 
>>> creates circular dependency. So it has to be included from 
>>> mm/arch_pgtable_test.c
>>
>> In fact it is <linux/highmem.h> that needs to be added, adding 
>> <asm/highmem.h> directly provokes build failure at link time.
>>
> 
> I get the following failure,
> 
> [    0.704685] ------------[ cut here ]------------
> [    0.709239] initcall arch_pgtable_tests_init+0x0/0x228 returned with 
> preemption imbalance

preempt_disable() is called from kmap_atomic() which is called from 
pte_alloc_map() via pte_offset_map().

pte_unmap() has to be called to release the mapped pte and re-enable 
preemtion.

Christophe

> [    0.717539] WARNING: CPU: 0 PID: 1 at init/main.c:952 
> do_one_initcall+0x18c/0x1d4
> [    0.724922] CPU: 0 PID: 1 Comm: swapper Not tainted 
> 5.3.0-rc7-s3k-dev-00880-g28fd02a838e5-dirty #2307
> [    0.734070] NIP:  c070e674 LR: c070e674 CTR: c001292c
> [    0.739084] REGS: df4a5dd0 TRAP: 0700   Not tainted 
> (5.3.0-rc7-s3k-dev-00880-g28fd02a838e5-dirty)
> [    0.747975] MSR:  00029032 <EE,ME,IR,DR,RI>  CR: 28000222  XER: 00000000
> [    0.754628]
> [    0.754628] GPR00: c070e674 df4a5e88 df4a0000 0000004e 0000000a 
> 00000000 000000ca 38207265
> [    0.754628] GPR08: 00001032 00000800 00000000 00000000 22000422 
> 00000000 c0004a7c 00000000
> [    0.754628] GPR16: 00000000 00000000 00000000 00000000 00000000 
> c0810000 c0800000 c0816f30
> [    0.754628] GPR24: c070dc20 c074702c 00000006 0000009c 00000000 
> c0724494 c074e140 00000000
> [    0.789339] NIP [c070e674] do_one_initcall+0x18c/0x1d4
> [    0.794435] LR [c070e674] do_one_initcall+0x18c/0x1d4
> [    0.799437] Call Trace:
> [    0.801867] [df4a5e88] [c070e674] do_one_initcall+0x18c/0x1d4 
> (unreliable)
> [    0.808694] [df4a5ee8] [c070e8c0] kernel_init_freeable+0x204/0x2dc
> [    0.814830] [df4a5f28] [c0004a94] kernel_init+0x18/0x110
> [    0.820107] [df4a5f38] [c00122ac] ret_from_kernel_thread+0x14/0x1c
> [    0.826220] Instruction dump:
> [    0.829161] 4beb1069 7d2000a6 61298000 7d200124 89210008 2f890000 
> 41be0048 3c60c06a
> [    0.836849] 38a10008 7fa4eb78 3863cacc 4b915115 <0fe00000> 4800002c 
> 81220070 712a0004
> [    0.844723] ---[ end trace 969d686308d40b33 ]---
> 
> Then starting init fails:
> 
> [    3.894074] Run /init as init process
> [    3.898403] Failed to execute /init (error -14)
> [    3.903009] Run /sbin/init as init process
> [    3.907172] Run /etc/init as init process
> [    3.911251] Run /bin/init as init process
> [    3.915513] Run /bin/sh as init process
> [    3.919471] Starting init: /bin/sh exists but couldn't execute it 
> (error -14)
> [    3.926732] Kernel panic - not syncing: No working init found.  Try 
> passing init= option to kernel. See Linux 
> Documentation/admin-guide/init.rst for guidance.
> [    3.940864] CPU: 0 PID: 1 Comm: init Tainted: G        W 
> 5.3.0-rc7-s3k-dev-00880-g28fd02a838e5-dirty #2307
> [    3.951165] Call Trace:
> [    3.953617] [df4a5ec8] [c002392c] panic+0x12c/0x320 (unreliable)
> [    3.959621] [df4a5f28] [c0004b8c] rootfs_mount+0x0/0x2c
> [    3.964849] [df4a5f38] [c00122ac] ret_from_kernel_thread+0x14/0x1c
> 
> 
> Christophe

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