linux-kernel - Re: [RFC v2 PATCH 7/8] mm: add the buddy system interface

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Date:	Tue, 30 Jun 2015 10:01:04 +0900
From:	Kamezawa Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	"Luck, Tony" <tony.luck@...el.com>,
	Xishi Qiu <qiuxishi@...wei.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...nel.org>,
	Hanjun Guo <guohanjun@...wei.com>,
	Xiexiuqi <xiexiuqi@...wei.com>, "leon@...n.nu" <leon@...n.nu>,
	"Hansen, Dave" <dave.hansen@...el.com>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	Vlastimil Babka <vbabka@...e.cz>, Mel Gorman <mgorman@...e.de>
CC:	Linux MM <linux-mm@...ck.org>, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC v2 PATCH 7/8] mm: add the buddy system interface

On 2015/06/30 8:11, Luck, Tony wrote:
>> @@ -814,7 +814,7 @@ int __init_memblock memblock_clear_hotplug(phys_addr_t base, phys_addr_t size)
>>    */
>>   int __init_memblock memblock_mark_mirror(phys_addr_t base, phys_addr_t size)
>>   {
>> -	system_has_some_mirror = true;
>> +	static_key_slow_inc(&system_has_mirror);
>>
>>   	return memblock_setclr_flag(base, size, 1, MEMBLOCK_MIRROR);
>>   }
>
> This generates some WARN_ON noise when called from efi_find_mirror():
>

It seems jump_label_init() is called after memory initialization. (init/main.c::start_kernel())
So, it may be difficut to use static_key function for our purpose because
kernel memory allocation may occur before jump_label is ready.

Thanks,
-Kame

> [    0.000000] e820: last_pfn = 0x7b800 max_arch_pfn = 0x400000000
> [    0.000000] ------------[ cut here ]------------
> [    0.000000] WARNING: CPU: 0 PID: 0 at kernel/jump_label.c:61 static_key_slow_inc+0x57/0xc0()
> [    0.000000] static_key_slow_inc used before call to jump_label_init
> [    0.000000] Modules linked in:
>
> [    0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted 4.1.0 #4
> [    0.000000] Hardware name: Intel Corporation BRICKLAND/BRICKLAND, BIOS BRHSXSD1.86B.0065.R01.1505011640 05/01/2015
> [    0.000000]  0000000000000000 ee366a8dff38f745 ffffffff81997d68 ffffffff816683b4
> [    0.000000]  0000000000000000 ffffffff81997dc0 ffffffff81997da8 ffffffff8107b0aa
> [    0.000000]  ffffffff81d48822 ffffffff81f281a0 0000000040000000 0000001fcb7a4000
> [    0.000000] Call Trace:
> [    0.000000]  [<ffffffff816683b4>] dump_stack+0x45/0x57
> [    0.000000]  [<ffffffff8107b0aa>] warn_slowpath_common+0x8a/0xc0
> [    0.000000]  [<ffffffff8107b135>] warn_slowpath_fmt+0x55/0x70
> [    0.000000]  [<ffffffff81660273>] ? memblock_add_range+0x175/0x19e
> [    0.000000]  [<ffffffff81176c57>] static_key_slow_inc+0x57/0xc0
> [    0.000000]  [<ffffffff81660655>] memblock_mark_mirror+0x19/0x33
> [    0.000000]  [<ffffffff81b12c18>] efi_find_mirror+0x59/0xdd
> [    0.000000]  [<ffffffff81afb8a6>] setup_arch+0x642/0xccf
> [    0.000000]  [<ffffffff81af3120>] ? early_idt_handler_array+0x120/0x120
> [    0.000000]  [<ffffffff81663480>] ? printk+0x55/0x6b
> [    0.000000]  [<ffffffff81af3120>] ? early_idt_handler_array+0x120/0x120
> [    0.000000]  [<ffffffff81af3d93>] start_kernel+0xe8/0x4eb
> [    0.000000]  [<ffffffff81af3120>] ? early_idt_handler_array+0x120/0x120
> [    0.000000]  [<ffffffff81af3120>] ? early_idt_handler_array+0x120/0x120
> [    0.000000]  [<ffffffff81af35ee>] x86_64_start_reservations+0x2a/0x2c
> [    0.000000]  [<ffffffff81af373c>] x86_64_start_kernel+0x14c/0x16f
> [    0.000000] ---[ end trace baa7fa0514e3bc58 ]---
> [    0.000000] ------------[ cut here ]------------
>
>
>
>
>


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