From: Chen Ridong <chenridong@huawei.com>

This patch adds cpus_excl_conflict() and mems_excl_conflict() helper
functions to improve code readability and maintainability. The exclusive
conflict checking follows these rules:

1. If either cpuset has the 'exclusive' flag set, their user_xcpus must
   not have any overlap.
2. If both cpusets are non-exclusive, their 'cpuset.cpus.exclusive' values
   must not intersect.
3. The 'cpuset.cpus' of one cpuset must not form a subset of another
   cpuset's 'cpuset.cpus.exclusive'.

Signed-off-by: Chen Ridong <chenridong@huawei.com>
---
 kernel/cgroup/cpuset.c | 62 ++++++++++++++++++++++--------------------
 1 file changed, 32 insertions(+), 30 deletions(-)

diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index 5dd1e9552000..5cfc53fe717c 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -584,6 +584,35 @@ static inline bool cpusets_are_exclusive(struct cpuset *cs1, struct cpuset *cs2)
 	return true;
 }
 
+static inline bool cpus_excl_conflict(struct cpuset *cs1, struct cpuset *cs2)
+{
+	/* One is exclusive, they must be exclusive */
+	if (is_cpu_exclusive(cs1) || is_cpu_exclusive(cs2))
+		return !cpusets_are_exclusive(cs1, cs2);
+
+	/* Exclusive_cpus can not have intersects*/
+	if (cpumask_intersects(cs1->exclusive_cpus, cs2->exclusive_cpus))
+		return true;
+
+	/* One cpus_allowed can not be a subset of another's cpuset.effective_cpus */
+	if (!cpumask_empty(cs1->cpus_allowed) &&
+	    cpumask_subset(cs1->cpus_allowed, cs2->exclusive_cpus))
+		return true;
+
+	if (!cpumask_empty(cs2->cpus_allowed) &&
+	    cpumask_subset(cs2->cpus_allowed, cs1->exclusive_cpus))
+		return true;
+
+	return false;
+}
+
+static inline bool mems_excl_conflict(struct cpuset *cs1, struct cpuset *cs2)
+{
+	if ((is_mem_exclusive(cs1) || is_mem_exclusive(cs2)))
+		return nodes_intersects(cs1->mems_allowed, cs2->mems_allowed);
+	return false;
+}
+
 /*
  * validate_change() - Used to validate that any proposed cpuset change
  *		       follows the structural rules for cpusets.
@@ -665,38 +694,11 @@ static int validate_change(struct cpuset *cur, struct cpuset *trial)
 	 */
 	ret = -EINVAL;
 	cpuset_for_each_child(c, css, par) {
-		bool txset, cxset;	/* Are exclusive_cpus set? */
-
 		if (c == cur)
 			continue;
-
-		txset = !cpumask_empty(trial->exclusive_cpus);
-		cxset = !cpumask_empty(c->exclusive_cpus);
-		if (is_cpu_exclusive(trial) || is_cpu_exclusive(c) ||
-		    (txset && cxset)) {
-			if (!cpusets_are_exclusive(trial, c))
-				goto out;
-		} else if (txset || cxset) {
-			struct cpumask *xcpus, *acpus;
-
-			/*
-			 * When just one of the exclusive_cpus's is set,
-			 * cpus_allowed of the other cpuset, if set, cannot be
-			 * a subset of it or none of those CPUs will be
-			 * available if these exclusive CPUs are activated.
-			 */
-			if (txset) {
-				xcpus = trial->exclusive_cpus;
-				acpus = c->cpus_allowed;
-			} else {
-				xcpus = c->exclusive_cpus;
-				acpus = trial->cpus_allowed;
-			}
-			if (!cpumask_empty(acpus) && cpumask_subset(acpus, xcpus))
-				goto out;
-		}
-		if ((is_mem_exclusive(trial) || is_mem_exclusive(c)) &&
-		    nodes_intersects(trial->mems_allowed, c->mems_allowed))
+		if (cpus_excl_conflict(trial, c))
+			goto out;
+		if (mems_excl_conflict(trial, c))
 			goto out;
 	}
 
-- 
2.34.1

On 8/28/25 8:56 AM, Chen Ridong wrote:
> From: Chen Ridong <chenridong@huawei.com>
>
> This patch adds cpus_excl_conflict() and mems_excl_conflict() helper
> functions to improve code readability and maintainability. The exclusive
> conflict checking follows these rules:
>
> 1. If either cpuset has the 'exclusive' flag set, their user_xcpus must
>     not have any overlap.
> 2. If both cpusets are non-exclusive, their 'cpuset.cpus.exclusive' values
>     must not intersect.
Do you mean "both cpusets are exclusive"?
> 3. The 'cpuset.cpus' of one cpuset must not form a subset of another
>     cpuset's 'cpuset.cpus.exclusive'.
>
> Signed-off-by: Chen Ridong <chenridong@huawei.com>
> ---
>   kernel/cgroup/cpuset.c | 62 ++++++++++++++++++++++--------------------
>   1 file changed, 32 insertions(+), 30 deletions(-)
>
> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
> index 5dd1e9552000..5cfc53fe717c 100644
> --- a/kernel/cgroup/cpuset.c
> +++ b/kernel/cgroup/cpuset.c
> @@ -584,6 +584,35 @@ static inline bool cpusets_are_exclusive(struct cpuset *cs1, struct cpuset *cs2)
>   	return true;
>   }
>   
> +static inline bool cpus_excl_conflict(struct cpuset *cs1, struct cpuset *cs2)
> +{
> +	/* One is exclusive, they must be exclusive */
The comment is hard to understand. Basically, if one cpuset has 
exclusive flag set (a v1 feature), they must be exclusive wrt each other.
> +	if (is_cpu_exclusive(cs1) || is_cpu_exclusive(cs2))
> +		return !cpusets_are_exclusive(cs1, cs2);
> +
> +	/* Exclusive_cpus can not have intersects*/
Grammatical mistake, better wording - "exclusive_cpus cannot intersect"
> +	if (cpumask_intersects(cs1->exclusive_cpus, cs2->exclusive_cpus))
> +		return true;
> +
> +	/* One cpus_allowed can not be a subset of another's cpuset.effective_cpus */
"cpus_allowed of one cpuset cannot be a subset of another cpuset's 
exclusive_cpus"
> +	if (!cpumask_empty(cs1->cpus_allowed) &&
> +	    cpumask_subset(cs1->cpus_allowed, cs2->exclusive_cpus))
> +		return true;
> +
> +	if (!cpumask_empty(cs2->cpus_allowed) &&
> +	    cpumask_subset(cs2->cpus_allowed, cs1->exclusive_cpus))
> +		return true;
> +
> +	return false;
> +}
> +
Cheers,
Longman

On 2025/8/30 3:29, Waiman Long wrote:
> 
> On 8/28/25 8:56 AM, Chen Ridong wrote:
>> From: Chen Ridong <chenridong@huawei.com>
>>
>> This patch adds cpus_excl_conflict() and mems_excl_conflict() helper
>> functions to improve code readability and maintainability. The exclusive
>> conflict checking follows these rules:
>>
>> 1. If either cpuset has the 'exclusive' flag set, their user_xcpus must
>>     not have any overlap.
>> 2. If both cpusets are non-exclusive, their 'cpuset.cpus.exclusive' values
>>     must not intersect.
> Do you mean "both cpusets are exclusive"?

Thank you Longman.

I meant that neither of the two cpusets has the "exclusive" flag set. Case 1 already handles
situations where one or both cpusets have the exclusive flag enabled.

>> 3. The 'cpuset.cpus' of one cpuset must not form a subset of another
>>     cpuset's 'cpuset.cpus.exclusive'.
>>
>> Signed-off-by: Chen Ridong <chenridong@huawei.com>
>> ---
>>   kernel/cgroup/cpuset.c | 62 ++++++++++++++++++++++--------------------
>>   1 file changed, 32 insertions(+), 30 deletions(-)
>>
>> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
>> index 5dd1e9552000..5cfc53fe717c 100644
>> --- a/kernel/cgroup/cpuset.c
>> +++ b/kernel/cgroup/cpuset.c
>> @@ -584,6 +584,35 @@ static inline bool cpusets_are_exclusive(struct cpuset *cs1, struct cpuset *cs2)
>>       return true;
>>   }
>>   +static inline bool cpus_excl_conflict(struct cpuset *cs1, struct cpuset *cs2)
>> +{
>> +    /* One is exclusive, they must be exclusive */
> The comment is hard to understand. Basically, if one cpuset has exclusive flag set (a v1 feature),
> they must be exclusive wrt each other.

My apologies for the earlier comment.

To quote your remark:
  "Basically, if one cpuset has the exclusive flag set (a v1 feature), they must be exclusive with
wrt to each other."

That is exactly what I meant. Although cpuset v2 does not expose a user interface to explicitly set
the exclusive flag, the flag will still be set internally when a partition is enabled with
update_partition_exclusive_flag function.

>> +    if (is_cpu_exclusive(cs1) || is_cpu_exclusive(cs2))
>> +        return !cpusets_are_exclusive(cs1, cs2);
>> +
>> +    /* Exclusive_cpus can not have intersects*/
> Grammatical mistake, better wording - "exclusive_cpus cannot intersect"
>> +    if (cpumask_intersects(cs1->exclusive_cpus, cs2->exclusive_cpus))
>> +        return true;
>> +
>> +    /* One cpus_allowed can not be a subset of another's cpuset.effective_cpus */
> "cpus_allowed of one cpuset cannot be a subset of another cpuset's exclusive_cpus"

Will update with next version.

>> +    if (!cpumask_empty(cs1->cpus_allowed) &&
>> +        cpumask_subset(cs1->cpus_allowed, cs2->exclusive_cpus))
>> +        return true;
>> +
>> +    if (!cpumask_empty(cs2->cpus_allowed) &&
>> +        cpumask_subset(cs2->cpus_allowed, cs1->exclusive_cpus))
>> +        return true;
>> +
>> +    return false;
>> +}
>> +
> Cheers,
> Longman

-- 
Best regards,
Ridong