Re: [PATCH 1/2] cgroup: cgroup_subsys[ssid] is never NULL

[Wei Yang]

On Mon, Nov 29, 2021 at 07:35:54AM -1000, Tejun Heo wrote:
>On Sat, Nov 27, 2021 at 02:59:18PM +0000, Wei Yang wrote:
>> When the check, (ssid) < CGROUP_SUBSYS_COUNT, passed, it means
>> cgroup_subsys[ssid] is defined to its proper value. It is not
>> necessary to use a true to enter the loop.
>...
>>  #define for_each_subsys(ss, ssid)					\
>>  	for ((ssid) = 0; (ssid) < CGROUP_SUBSYS_COUNT &&		\
>> -	     (((ss) = cgroup_subsys[ssid]) || true); (ssid)++)
>> +	     ((ss) = cgroup_subsys[ssid]); (ssid)++)
>
>So, now the compiler has to test whether ss is NULL or not before each
>iteration even though we know that it's never NULL. The whole point of that
>"|| true" is telling the compiler that the pointer is never NULL.
>

That's interesting. Thanks.

>Thanks.
>
>-- 
>tejun

-- 
Wei Yang
Help you, Help me