On 2025/11/17 18:00, Sun Shaojie wrote:
On 2025/11/17 15:45, Chen Ridong Wrote:
On 2025/11/17 9:57, Sun Shaojie wrote:
In cgroup v2, a mutual overlap check is required when at least one of two cpusets is exclusive. However, this check should be relaxed and limited to cases where both cpusets are exclusive.
This patch ensures that for sibling cpusets A1 (exclusive) and B1 (non-exclusive), change B1 cannot affect A1's exclusivity.
for example. Assume a machine has 4 CPUs (0-3).
root cgroup / \ A1 B1
Case 1: Table 1.1: Before applying the patch Step | A1's prstate | B1'sprstate | #1> echo "0-1" > A1/cpuset.cpus | member | member | #2> echo "root" > A1/cpuset.cpus.partition | root | member | #3> echo "0" > B1/cpuset.cpus | root invalid | member |
After step #3, A1 changes from "root" to "root invalid" because its CPUs (0-1) overlap with those requested by B1 (0-3). However, B1 can actually
B1 (0-3) --> B1(0) ?
Sorry, that was a typo. It should indeed be B1 (0).
use CPUs 2-3(from B1's parent), so it would be more reasonable for A1 to remain as "root."
Table 1.2: After applying the patch Step | A1's prstate | B1'sprstate | #1> echo "0-1" > A1/cpuset.cpus | member | member | #2> echo "root" > A1/cpuset.cpus.partition | root | member | #3> echo "0" > B1/cpuset.cpus | root | member |
All other cases remain unaffected. For example, cgroup-v1, both A1 and B1 are exclusive or non-exlusive.
Signed-off-by: Sun Shaojie sunshaojie@kylinos.cn
kernel/cgroup/cpuset-internal.h | 3 ++ kernel/cgroup/cpuset-v1.c | 20 +++++++++ kernel/cgroup/cpuset.c | 43 ++++++++++++++----- .../selftests/cgroup/test_cpuset_prs.sh | 5 ++- 4 files changed, 58 insertions(+), 13 deletions(-)
diff --git a/kernel/cgroup/cpuset-internal.h b/kernel/cgroup/cpuset-internal.h index 337608f408ce..c53111998432 100644 --- a/kernel/cgroup/cpuset-internal.h +++ b/kernel/cgroup/cpuset-internal.h @@ -292,6 +292,7 @@ void cpuset1_hotplug_update_tasks(struct cpuset *cs, struct cpumask *new_cpus, nodemask_t *new_mems, bool cpus_updated, bool mems_updated); int cpuset1_validate_change(struct cpuset *cur, struct cpuset *trial); +bool cpuset1_cpus_excl_conflict(struct cpuset *cs1, struct cpuset *cs2); #else static inline void fmeter_init(struct fmeter *fmp) {} static inline void cpuset1_update_task_spread_flags(struct cpuset *cs, @@ -302,6 +303,8 @@ static inline void cpuset1_hotplug_update_tasks(struct cpuset *cs, bool cpus_updated, bool mems_updated) {} static inline int cpuset1_validate_change(struct cpuset *cur, struct cpuset *trial) { return 0; } +static inline bool cpuset1_cpus_excl_conflict(struct cpuset *cs1,
struct cpuset *cs2) {return false; }#endif /* CONFIG_CPUSETS_V1 */ #endif /* __CPUSET_INTERNAL_H */ diff --git a/kernel/cgroup/cpuset-v1.c b/kernel/cgroup/cpuset-v1.c index 12e76774c75b..5c1296bf6a34 100644 --- a/kernel/cgroup/cpuset-v1.c +++ b/kernel/cgroup/cpuset-v1.c @@ -373,6 +373,26 @@ int cpuset1_validate_change(struct cpuset *cur, struct cpuset *trial) return ret; } +/*
- cpuset1_cpus_excl_conflict() - Check if two cpusets have exclusive CPU conflicts
to legacy (v1)
- @cs1: first cpuset to check
- @cs2: second cpuset to check
- Returns: true if CPU exclusivity conflict exists, false otherwise
- If either cpuset is CPU exclusive, their allowed CPUs cannot intersect.
- */
+bool cpuset1_cpus_excl_conflict(struct cpuset *cs1, struct cpuset *cs2) +{
- if (is_cpu_exclusive(cs1) || is_cpu_exclusive(cs2))
if (cpumask_intersects(cs1->cpus_allowed,cs2->cpus_allowed))return true;- return false;
+}
#ifdef CONFIG_PROC_PID_CPUSET /*
- proc_cpuset_show()
diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c index 52468d2c178a..0fd803612513 100644 --- a/kernel/cgroup/cpuset.c +++ b/kernel/cgroup/cpuset.c @@ -580,35 +580,56 @@ static inline bool cpusets_are_exclusive(struct cpuset *cs1, struct cpuset *cs2) /**
- cpus_excl_conflict - Check if two cpusets have exclusive CPU conflicts
- @cs1: first cpuset to check
- @cs2: second cpuset to check
- @cs1: current cpuset to check
- @cs2: cpuset involved in the check
- Returns: true if CPU exclusivity conflict exists, false otherwise
- Conflict detection rules:
- If either cpuset is CPU exclusive, they must be mutually exclusive
- For cgroup-v1:
see cpuset1_cpus_excl_conflict()
- For cgroup-v2:
- If cs1 is exclusive, cs1 and cs2 must be mutually exclusive
- exclusive_cpus masks cannot intersect between cpusets
- The allowed CPUs of one cpuset cannot be a subset of another's exclusive CPUs
- If cs2 is exclusive, cs2's allowed CPUs cannot be a subset of cs1's exclusive CPUs
- if cs1 and cs2 are not exclusive, the allowed CPUs of one cpuset cannot be a subset
*/
- of another's exclusive CPUs
The revised conflict detection rules are confusing to me. I thought cs1 and cs2 should be treated symmetrically, but that doesn’t seem to be the case here.
Shouldn’t the following rule apply regardless of whether cs1 or cs2 is exclusive: "The allowed CPUs of one cpuset cannot be a subset of another's exclusive CPUs"?
Certainly, this rule applies regardless of whether cs1 or cs2 is exclusive, and the current implementation already handles it this way. The following two cases cover this rule. "1. If cs1 is exclusive, cs1 and cs2 must be mutually exclusive" "3. If cs2 is exclusive, cs2's allowed CPUs cannot be a subset of cs1's exclusive CPUs"
I believe this function should return the same result regardless of whether it is called as cpus_excl_conflict(A1, B1) or cpus_excl_conflict(B1, A1), which means cs1 and cs2 should be treated symmetrically. However, since cs1 and cs2 are handled differently, it is difficult to convince me that this implementation is correct.
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))
- /* For cgroup-v1 */
- if (!cpuset_v2())
return cpuset1_cpus_excl_conflict(cs1, cs2);- /* If cs1 are exclusive, check if they are mutually exclusive */
- if (is_cpu_exclusive(cs1)) return !cpusets_are_exclusive(cs1, cs2);
- /* The following check applies when either
* both cs1 and cs2 are non-exclusive，or* only cs2 is exclusive.*/- /* Exclusive_cpus cannot intersect */ if (cpumask_intersects(cs1->exclusive_cpus, cs2->exclusive_cpus)) return true;
- /* The 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;
- /* cs2's allowed CPUs cannot be a subset of cs1's exclusive CPUs */ if (!cpumask_empty(cs2->cpus_allowed) && cpumask_subset(cs2->cpus_allowed, cs1->exclusive_cpus)) return true;
- /* If cs2 is exclusive, check finished here */
- if (is_cpu_exclusive(cs2))
return false;- /* The following check applies only if both cs1 and cs2 are non-exclusive. */
- /* cs1's allowed CPUs cannot be a subset of cs1's exclusive CPUs */
- if (!cpumask_empty(cs1->cpus_allowed) &&
cpumask_subset(cs1->cpus_allowed, cs2->exclusive_cpus))return true;- return false;
}
From your commit message, it appears you intend to modify "if (is_cpu_exclusive(cs1) || is_cpu_exclusive(cs2))" to "if (is_cpu_exclusive(cs1) && is_cpu_exclusive(cs2))".
However, I’m having trouble following the change.
The current modification specifically addresses the scenario where one cpuset A1 is exclusive and its sibling cpuset B1 is non-exclusive. The goal is to ensure that when the non-exclusive cpuset B1 modifies its own "cpuset.cpus" or "cpuset.cpus.exclusive", it does not cause A1 to change from exclusive to non-exclusive.
The following three scenarios are not affected by this patch: 1.both A1 and B1 are exclusive. 2.both A1 and B1 are non-exclusive. 3.A1 is exclusive, B1 is non-exclusive, change "cpuset.cpus" or "cpuset.cpus.exclusive" of A1.
diff --git a/tools/testing/selftests/cgroup/test_cpuset_prs.sh b/tools/testing/selftests/cgroup/test_cpuset_prs.sh index a17256d9f88a..b848bc0729cf 100755 --- a/tools/testing/selftests/cgroup/test_cpuset_prs.sh +++ b/tools/testing/selftests/cgroup/test_cpuset_prs.sh @@ -388,10 +388,11 @@ TEST_MATRIX=( " C0-1:S+ C1 . C2-3 . P2 . . 0 A1:0-1|A2:1 A1:P0|A2:P-2" " C0-1:S+ C1:P2 . C2-3 P1 . . . 0 A1:0|A2:1 A1:P1|A2:P2 0-1|1"
- # A non-exclusive cpuset.cpus change will invalidate partition and its siblings
- # A non-exclusive cpuset.cpus change will not invalidate its siblings partition.
- # But a exclusive cpuset.cpus change will invalidate itself. " C0-1:P1 . . C2-3 C0-2 . . . 0 A1:0-2|B1:2-3 A1:P-1|B1:P0" " C0-1:P1 . . P1:C2-3 C0-2 . . . 0 A1:0-2|B1:2-3 A1:P-1|B1:P-1"
- " C0-1 . . P1:C2-3 C0-2 . . . 0 A1:0-2|B1:2-3 A1:P0|B1:P-1"
- " C0-1 . . P1:C2-3 C0-2 . . . 0 A1:0-1|B1:2-3 A1:P0|B1:P1"
# cpuset.cpus can overlap with sibling cpuset.cpus.exclusive but not subsumed by it " C0-3 . . C4-5 X5 . . . 0 A1:0-3|B1:4-5"