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cgroup/cpuset: Fix wrong check in update_parent_subparts_cpumask()

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It was found that the check to see if a partition could use up all
the cpus from the parent cpuset in update_parent_subparts_cpumask()
was incorrect. As a result, it is possible to leave parent with no
effective cpu left even if there are tasks in the parent cpuset. This
can lead to system panic as reported in [1].

Fix this probem by updating the check to fail the enabling the partition
if parent's effective_cpus is a subset of the child's cpus_allowed.

Also record the error code when an error happens in update_prstate()
and add a test case where parent partition and child have the same cpu
list and parent has task. Enabling partition in the child will fail in
this case.

[1] https://www.spinics.net/lists/cgroups/msg36254.html

Fixes: f0af1bfc27 ("cgroup/cpuset: Relax constraints to partition & cpus changes")
Cc: stable@vger.kernel.org # v6.1
Reported-by: Srinivas Pandruvada <srinivas.pandruvada@intel.com>
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Waiman Long 2023-01-31 10:48:03 -05:00 committed by Tejun Heo
parent 58706f7fb0
commit e5ae880384
2 changed files with 3 additions and 1 deletions
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3
kernel/cgroup/cpuset.c
View file

@ -1346,7 +1346,7 @@ static int update_parent_subparts_cpumask(struct cpuset *cs, int cmd,
* A parent can be left with no CPU as long as there is no
* task directly associated with the parent partition.
*/
if (!cpumask_intersects(cs->cpus_allowed, parent->effective_cpus) &&
if (cpumask_subset(parent->effective_cpus, cs->cpus_allowed) &&
partition_is_populated(parent, cs))
return PERR_NOCPUS;
@ -2324,6 +2324,7 @@ static int update_prstate(struct cpuset *cs, int new_prs)
new_prs = -new_prs;
spin_lock_irq(&callback_lock);
cs->partition_root_state = new_prs;
WRITE_ONCE(cs->prs_err, err);
spin_unlock_irq(&callback_lock);
/*
* Update child cpusets, if present.

1
tools/testing/selftests/cgroup/test_cpuset_prs.sh
View file

@ -268,6 +268,7 @@ TEST_MATRIX=(
# Taking away all CPUs from parent or itself if there are tasks
# will make the partition invalid.
" S+ C2-3:P1:S+ C3:P1 . . T C2-3 . . 0 A1:2-3,A2:2-3 A1:P1,A2:P-1"
" S+ C3:P1:S+ C3 . . T P1 . . 0 A1:3,A2:3 A1:P1,A2:P-1"
" S+ $SETUP_A123_PARTITIONS . T:C2-3 . . . 0 A1:2-3,A2:2-3,A3:3 A1:P1,A2:P-1,A3:P-1"
" S+ $SETUP_A123_PARTITIONS . T:C2-3:C1-3 . . . 0 A1:1,A2:2,A3:3 A1:P1,A2:P1,A3:P1"