linux-kernel - Re: [PATCH V1] mm/damon: Modify damon_rand() macro to static inline function

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Message-ID: <08a13269-e3eb-219f-79bb-8d0153714c69@linux.alibaba.com>
Date:   Mon, 6 Dec 2021 20:48:18 +0800
From:   Xin Hao <xhao@...ux.alibaba.com>
To:     SeongJae Park <sj@...nel.org>
Cc:     akpm@...ux-foundation.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH V1] mm/damon: Modify damon_rand() macro to static inline
 function


On 12/6/21 8:45 PM, SeongJae Park wrote:
> On Mon, 6 Dec 2021 20:41:29 +0800 Xin Hao <xhao@...ux.alibaba.com> wrote:
>
>> The damon_rand() func can not be implemented as a macro.
>> Example:
>> 	damon_rand(a++, b);
>> The value of 'a' will be incremented twice, This is obviously
>> unreasonable, So there fix it.
>>
>> Fixes: b9a6ac4e4ede ("mm/damon: adaptively adjust regions")
>> Reported-by: Andrew Morton <akpm@...ux-foundation.org>
>> Signed-off-by: Xin Hao <xhao@...ux.alibaba.com>
>> ---
>>   include/linux/damon.h | 5 ++++-
>>   1 file changed, 4 insertions(+), 1 deletion(-)
>>
>> diff --git a/include/linux/damon.h b/include/linux/damon.h
>> index c6df025d8704..bc9c8932b1e8 100644
>> --- a/include/linux/damon.h
>> +++ b/include/linux/damon.h
>> @@ -19,7 +19,10 @@
>>   #define DAMOS_MAX_SCORE		(99)
>>
>>   /* Get a random number in [l, r) */
>> -#define damon_rand(l, r) (l + prandom_u32_max(r - l))
>> +static inline unsigned long damon_rand(unsigned long l, unsigned long r)
>> +{
>> +	return l + (r - l);
> Seems prandom_u32_max() is missed?

Sorry, my fault, i write a simple test case like this, but i forgot to 
correct in patch, i will send a new one.

#include <stdio.h>

#define damon_rand(l, r) (l + (r - l))
static inline long damon_rand1(int l, int r)
{
         return l + (r - l);
}

int main(void)
{

         int a = 0;
         int b = 0;
         damon_rand(a++, 4);
         damon_rand1(b++, 4);

         printf("a is %d \n", a);
         printf("b is %d \n", b);

         return 0;
}

>
>
> Thanks,
> SJ
>
>> +}
>>
>>   /**
>>    * struct damon_addr_range - Represents an address region of [@start, @end).
>> --
>> 2.31.0

-- 
Best Regards!
Xin Hao