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cgroup/cpuset: Prevent leakage of isolated CPUs into sched domains

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BugLink: https://bugs.launchpad.net/bugs/2106770

[ Upstream commit 9b496a8bbed9cc292b0dfd796f38ec58b6d0375f ]

Isolated CPUs are not allowed to be used in a non-isolated partition.
The only exception is the top cpuset which is allowed to contain boot
time isolated CPUs.

Commit ccac8e8de99c ("cgroup/cpuset: Fix remote root partition creation
problem") introduces a simplified scheme of including only partition
roots in sched domain generation. However, it does not properly account
for this exception case. This can result in leakage of isolated CPUs
into a sched domain.

Fix it by making sure that isolated CPUs are excluded from the top
cpuset before generating sched domains.

Also update the way the boot time isolated CPUs are handled in
test_cpuset_prs.sh to make sure that those isolated CPUs are really
isolated instead of just skipping them in the tests.

Fixes: ccac8e8de99c ("cgroup/cpuset: Fix remote root partition creation problem")
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
[diewald: drop changes to the selftests/cgroup/test_cpuset_prs.sh test
since the script is very different compared to 6.10+]
Signed-off-by: Manuel Diewald <manuel.diewald@canonical.com>
Signed-off-by: Mehmet Basaran <mehmet.basaran@canonical.com>
This commit is contained in:
Waiman Long
2024-12-05 14:51:01 -05:00
committed by Mehmet Basaran
parent b4c31236c0
commit de7ba6b935
1 changed files with 9 additions and 1 deletions
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kernel/cgroup/cpuset.c
+9 -1
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@@ -1125,7 +1125,15 @@ restart:
*/
if (cgrpv2) {
for (i = 0; i < ndoms; i++) {
cpumask_copy(doms[i], csa[i]->effective_cpus);
/*
* The top cpuset may contain some boot time isolated
* CPUs that need to be excluded from the sched domain.
*/
if (csa[i] == &top_cpuset)
cpumask_and(doms[i], csa[i]->effective_cpus,
housekeeping_cpumask(HK_TYPE_DOMAIN));
else
cpumask_copy(doms[i], csa[i]->effective_cpus);
if (dattr)
dattr[i] = SD_ATTR_INIT;
}