Re: [Xen-devel] [PATCH 02/16] x86: fix: make atomic_read() param const

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 12/07/16 06:11, Corneliu ZUZU wrote:
> Hi Andrew,
>
> On 7/11/2016 6:18 PM, Andrew Cooper wrote:
>> On 09/07/16 05:12, Corneliu ZUZU wrote:
>>> This wouldn't let me make a param of a function that used
>>> atomic_read() const.
>>>
>>> Signed-off-by: Corneliu ZUZU <czuzu@xxxxxxxxxxxxxxx>
>> This is a good improvement, but you must make an identical adjustment to
>> the arm code, otherwise you will end up with subtle build failures.
>
> Right, didn't even realize it was X86-specific.

It isn't x86 specific.  (Which is what I presume you meant to say.)

>
>>
>> If you are really feeling up to it, having a common xen/atomic.h with
>>
>> typedef struct { int counter; } atomic_t;
>> #define ATOMIC_INIT(i) { (i) }
>>
>> and some prototypes such as:
>>
>> static inline int atomic_read(const atomic_t *v);
>>
>> would be great, but this looks like it has the possibility to turn into
>> a rats nest.  If it does, then just doubling up this code for arm is ok.
>>
>> ~Andrew
>
> Yes, that might be more complicated than we expect and I don't know if
> making code such as this common would be a good idea, usually these
> functions are always architecture-specific.

I only suggested making the prototype common, not the implementation. 
As such, the issue you accidentally introduced would become a hard build
failure on affected architectures, rather than a subtle build failure in
common code at some point in the future.

~Andrew

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