在 2026/9/20 16:23, Hui Peng 写道:
> Commit 6da580ec656a ("cgroup/cpuset: Don't allow creation of local
> partition over a remote one") added a check in update_prstate() to reject
> creating a top-level local partition whose cs->exclusive_cpus intersects
> subpartitions_cpus.
>
> However, two paths still allow overlapping exclusive CPU ownership between
> a top-level local partition and a remote partition or sibling:
>
> 1. If a top-level cgroup A1 has cpuset.cpus.exclusive set, is first set to
> "root" while cpuset.cpus is empty (becoming "root invalid"), has a
> child A1/A2 enabled as a remote partition on those exclusive CPUs, and
> then receives CPUs via A1/cpuset.cpus, update_cpumasks_hier() calls
> validate_partition() without going through update_prstate(). Because
> validate_partition() does not check trialcs->exclusive_cpus against
> subpartitions_cpus, A1 transitions from "root invalid" to a valid local
> partition over the existing remote partition A1/A2 and triggers:
>
> WARNING: kernel/cgroup/cpuset.c:1866 at
> update_parent_effective_cpumask+0x54a/0x8a0
>
> 2. In cpus_excl_conflict(), when a valid local partition A1 uses implicit
> exclusive CPUs (cpuset.cpus set without cpuset.cpus.exclusive, so
> sibling->exclusive_cpus is empty while sibling->effective_xcpus is
> populated), a sibling cgroup B1 can still set cpuset.cpus.exclusive on
> the same CPUs because cpus_excl_conflict() only checks
> sibling->exclusive_cpus.
>
> Fix these issues by:
> - Checking trialcs->exclusive_cpus against subpartitions_cpus in
> validate_partition() when !is_partition_valid(cs).
> - Falling back to sibling->effective_xcpus in cpus_excl_conflict() when
> sibling->exclusive_cpus is empty.
> - Adding regression test cases for both paths to
> tools/testing/selftests/cgroup/test_cpuset_prs.sh.
>
> Tested in QEMU on Linux 7.3.0-rc3 using
> tools/testing/selftests/cgroup/test_cpuset_prs.sh.
>
> Fixes: 6da580ec656a ("cgroup/cpuset: Don't allow creation of local partition
> over a remote one")
I think this patch is still missing a Fixes: tag for the
cpus_excl_conflict() change.
The validate_partition() change can be covered by 6da580ec656a.
However, the sibling CPU ownership issue fixed in cpus_excl_conflict()
was introduced by the following commit:
Fixes: 2a3602030d80 ("cgroup/cpuset: Don't invalidate sibling partitions on
cpuset.cpus conflict")
Thanks,
Guopeng
> Cc: [email protected]
> Signed-off-by: Hui Peng <[email protected]>
> ---
> Changes in v2:
> - Split from the remote_partition_enable() fix into patch 2/2.
> - Check trialcs->exclusive_cpus (rather than effective_xcpus) in
> validate_partition() when !is_partition_valid(cs) so sibling local
> partitions with overlapping cpuset.cpus continue to share remaining
> available CPUs as expected by test_cpuset_prs.sh.
> - Add regression tests to tools/testing/selftests/cgroup/test_cpuset_prs.sh.
>
> kernel/cgroup/cpuset.c | 9 ++++++++-
> tools/testing/selftests/cgroup/test_cpuset_prs.sh | 3 +++
> 2 files changed, 11 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
> index 7381fa8502e7..f46a51f07938 100644
> --- a/kernel/cgroup/cpuset.c
> +++ b/kernel/cgroup/cpuset.c
> @@ -713,7 +713,10 @@ static inline bool cpus_excl_conflict(struct cpuset
> *trial, struct cpuset *sibli
> return true;
>
> /* Exclusive_cpus cannot intersect */
> - return cpumask_intersects(trial->exclusive_cpus,
> sibling->exclusive_cpus);
> + return cpumask_intersects(trial->exclusive_cpus,
> + cpumask_empty(sibling->exclusive_cpus)
> + ? sibling->effective_xcpus
> + : sibling->exclusive_cpus);
> }
>
> static inline bool mems_excl_conflict(struct cpuset *cs1, struct cpuset *cs2)
> @@ -2415,6 +2418,10 @@ static enum prs_errcode validate_partition(struct
> cpuset *cs, struct cpuset *tri
> if (cpumask_empty(trialcs->effective_xcpus))
> return PERR_INVCPUS;
>
> + if ((parent == &top_cpuset) && !is_partition_valid(cs) &&
> + cpumask_intersects(trialcs->exclusive_cpus, subpartitions_cpus))
> + return PERR_REMOTE;
> +
> if (prstate_housekeeping_conflict(trialcs->partition_root_state,
> trialcs->effective_xcpus))
> return PERR_HKEEPING;
> diff --git a/tools/testing/selftests/cgroup/test_cpuset_prs.sh
> b/tools/testing/selftests/cgroup/test_cpuset_prs.sh
> index b732078bf319..f62155cf6162 100755
> --- a/tools/testing/selftests/cgroup/test_cpuset_prs.sh
> +++ b/tools/testing/selftests/cgroup/test_cpuset_prs.sh
> @@ -321,6 +321,8 @@ TEST_MATRIX=(
> " C1-3:P2 X4:P2 . . . X3:P2 . . 0
> A1:1-2|XA1:1-3|A2:3:XA2:3 A1:P2|A2:P2 1-3"
> " C0-3:P2 . . C4-6 C0-4 . . . 0
> A1:0-4|B1:5-6 A1:P2|B1:P0"
> " C0-3:P2 . . C4-6 C0-4:C0-3 . . . 0
> A1:0-3|B1:4-6 A1:P2|B1:P0 0-3"
> + " X1-3:P1 CX2-3:P2 . . C1-3 . . . 0
> A1:1|A2:2-3|XA2:2-3 \
> +
> A1:P-1|A2:P2 2-3"
>
> # Local partition invalidation tests
> " C0-3:X1-3:P2 C1-3:X2-3:P2 C2-3:X3:P2 \
> @@ -443,6 +445,7 @@ TEST_MATRIX=(
>
> # Changes to cpuset.cpus.exclusive that violate exclusivity rule is
> rejected
> " C0-3 . . C4-5 X0-3 . . X3-5 1
> A1:0-3|B1:4-5"
> + " C0-3:P1 . . C4-5 . . . X3-5 1
> A1:0-3|B1:4-5 A1:P1|B1:P0"
>
> # cpuset.cpus.exclusive cannot be set to a superset of sibling's
> cpuset.cpus
> " C0-3 . . C4-5 X3-5 . . . 1
> A1:0-3|B1:4-5"
