Re: [PATCH v1] cpuset: Avoid unnecessary partition invalidation

[Waiman Long <llong@redhat.com>]

On 11/12/25 10:33 PM, Sun Shaojie wrote:
> The reviewer mentioned they couldn't see my original patch, so I'm
> re-quoting the key changes below for clarity:
>
>> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
>> index 52468d2c178a..e0d27c9a101a 100644
>> --- a/kernel/cgroup/cpuset.c
>> +++ b/kernel/cgroup/cpuset.c
>> @@ -586,14 +586,14 @@ static inline bool cpusets_are_exclusive(struct cpuset *cs1, struct cpuset *cs2)
>>   * Returns: true if CPU exclusivity conflict exists, false otherwise
>>   *
>>   * Conflict detection rules:
>> - * 1. If either cpuset is CPU exclusive, they must be mutually exclusive
>> + * 1. If both cpusets are exclusive, they must be mutually exclusive
>>   * 2. exclusive_cpus masks cannot intersect between cpusets
>>   * 3. The allowed CPUs of one cpuset cannot be a subset of another's exclusive CPUs
>>   */
>> static inline bool cpus_excl_conflict(struct cpuset *cs1, struct cpuset *cs2)
>> {
>> -	/* If either cpuset is exclusive, check if they are mutually exclusive */
>> -	if (is_cpu_exclusive(cs1) || is_cpu_exclusive(cs2))
>> +	/* If both cpusets are exclusive, check if they are mutually exclusive */
>> +	if (is_cpu_exclusive(cs1) && is_cpu_exclusive(cs2))
>> 		return !cpusets_are_exclusive(cs1, cs2);
>>
>> 	/* Exclusive_cpus cannot intersect */
> Here are the main changes, where the conflict check for step #6 in Table 2
> is performed. And these changes have no effect on cgroup v1.

cpus_excl_conflict() is called by validate_change() which is used for 
both v1 and v2.

Cheers,
Longman