linux-kernel - Re: "resource: provide new functions to walk through resources" breaks UML

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Date:	Mon, 11 Aug 2014 21:18:08 +0200
From:	Richard Weinberger <richard@....at>
To:	Vivek Goyal <vgoyal@...hat.com>
CC:	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	user-mode-linux-devel <user-mode-linux-devel@...ts.sourceforge.net>,
	sahne@...0.at
Subject: Re: "resource: provide new functions to walk through resources" breaks
 UML

Am 11.08.2014 20:44, schrieb Vivek Goyal:
> On Mon, Aug 11, 2014 at 02:25:56PM +0200, Richard Weinberger wrote:
>> Hi Vivek,
>>
>> Am 11.08.2014 14:22, schrieb Vivek Goyal:
>>> On Sun, Aug 10, 2014 at 06:56:14PM +0200, Richard Weinberger wrote:
>>>> Hi Vivek,
>>>>
>>>> Daniel Walter reported that UML is currently broken.
>>>> The offending commit is:
>>>>
>>>
>>> Hi Richard,
>>>
>>> Thanks for pointing it out. I will look into it.
>>>
>>> Would you have link to the report Daniel sent. I am interested in 
>>> looking at backtrace.
>>
>> he reported it on IRC to me.
>>
>> Here is a backtrace:
>> RIP: 0033:[<0000000060039b9f>]
>> RSP: 0000000081459da0  EFLAGS: 00010202
>> RAX: 0000000000000000 RBX: 00000000219b3fff RCX: 000000006010d1d9
>> RDX: 0000000000000001 RSI: 00000000602dfb94 RDI: 0000000081459df8
>> RBP: 0000000081459de0 R08: 00000000601b59f4 R09: ffffffff0000ff00
>> R10: ffffffff0000ff00 R11: 0000000081459e88 R12: 0000000081459df8
>> R13: 00000000219b3fff R14: 00000000602dfb94 R15: 0000000000000000
>> Kernel panic - not syncing: Segfault with no mm
>> CPU: 0 PID: 1 Comm: swapper Not tainted 3.16.0-10454-g58d08e3 #13
>> Stack:
>>  00000000 000080d0 81459df0 219b3fff
>>  81459e70 6010d1d9 ffffffff 6033e010
>>  81459e50 6003a269 81459e30 00000000
>> Call Trace:
>>  [<6010d1d9>] ? kclist_add_private+0x0/0xe7
>>  [<6003a269>] walk_system_ram_range+0x61/0xb7
>>  [<6000e859>] ? proc_kcore_init+0x0/0xf1
>>  [<6010d574>] kcore_update_ram+0x4c/0x168
>>  [<6010d72e>] ? kclist_add+0x0/0x2e
>>  [<6000e943>] proc_kcore_init+0xea/0xf1
>>  [<6000e859>] ? proc_kcore_init+0x0/0xf1
>>  [<6000e859>] ? proc_kcore_init+0x0/0xf1
>>  [<600189f0>] do_one_initcall+0x13c/0x204
>>  [<6004ca46>] ? parse_args+0x1df/0x2e0
>>  [<6004c82d>] ? parameq+0x0/0x3a
>>  [<601b5990>] ? strcpy+0x0/0x18
>>  [<60001e1a>] kernel_init_freeable+0x240/0x31e
>>  [<6026f1c0>] kernel_init+0x12/0x148
>>  [<60019fad>] new_thread_handler+0x81/0xa3
>>
>> RIP is at kernel/resource.c:66.
> 
> Hi Richard,
> 
> Can you please give the attached patch a try and see if it fixes the UML
> issue.
> 
> I noticed that previous code had a for() loop which will not execute
> if p was null. I have resorted back to same code now. 

Looks good!

Reported-by: Daniel Walter <sahne@...0.at>
Tested-by: Richard Weinberger <richard@....at>

Thanks,
//richard
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