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Re: [XEN][RFC PATCH v4 10/16] asm/smp.h: move cpu related function to asm/cpu.h
- To: Vikram Garhwal <vikram.garhwal@xxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Thu, 8 Dec 2022 09:18:46 +0100
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- Cc: sstabellini@xxxxxxxxxx, Luca.Fancellu@xxxxxxx, Bertrand Marquis <bertrand.marquis@xxxxxxx>, Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, George Dunlap <george.dunlap@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, Julien Grall <julien@xxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx
- Delivery-date: Thu, 08 Dec 2022 08:18:57 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 07.12.2022 20:39, Vikram Garhwal wrote:
> Hi Julien
>
> On 12/7/22 8:28 AM, Julien Grall wrote:
>> Hi Vikram,
>>
>> On 07/12/2022 06:18, Vikram Garhwal wrote:
>>> Dynamic programming ops will modify the dt_host and there might be other
>>> function which are browsing the dt_host at the same time. To avoid
>>> the race
>>> conditions, adding rwlock for browsing the dt_host. But adding rwlock in
>>> device_tree.h causes following circular dependency:
>>> device_tree.h->rwlock.h->smp.h->asm/smp.h->device_tree.h
>>>
>>> Inside arch/arm/include/asm/smp.h, there is one function which needs
>>> device_tree.h, moved the cpu related function to a new file:
>>> arch/arm/include/asm/cpu.h
>>
>> Given there is only one function, I don't really see the benefits of
>> splitting smp.h and then adding #ifdef CONFIG_ARM in the common code.
>>
>> Instead, it would be better if we don't include device_tree.h in the
>> header but in the c files that need to call arch_cpu_init() and
>> forward declare dt_device_node.
>>
> This was my initial approach also and there were less changes(compare to
> my v4) but then though someone might have issues with forward
> declaration of dt_device_node in smp.h.
We use forward declarations of struct/union is many places, precisely to
limit dependencies among headers.
Jan
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