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Message-ID: <20240805013019.724300-3-longman@redhat.com>
Date: Sun, 4 Aug 2024 21:30:16 -0400
From: Waiman Long <longman@...hat.com>
To: Tejun Heo <tj@...nel.org>,
Zefan Li <lizefan.x@...edance.com>,
Johannes Weiner <hannes@...xchg.org>,
Michal Koutný <mkoutny@...e.com>,
Shuah Khan <shuah@...nel.org>
Cc: linux-kernel@...r.kernel.org,
cgroups@...r.kernel.org,
linux-kselftest@...r.kernel.org,
Chen Ridong <chenridong@...wei.com>,
Waiman Long <longman@...hat.com>
Subject: [PATCH-cgroup 2/5] cgroup/cpuset: Clear effective_xcpus on cpus_allowed clearing only if cpus.exclusive not set
Commit e2ffe502ba45 ("cgroup/cpuset: Add cpuset.cpus.exclusive for
v2") adds a user writable cpuset.cpus.exclusive file for setting
exclusive CPUs to be used for the creation of partitions. Since then
effective_xcpus depends on both the cpuset.cpus and cpuset.cpus.exclusive
setting. If cpuset.cpus.exclusive is set, effective_xcpus will depend
only on cpuset.cpus.exclusive. When it is not set, effective_xcpus
will be set according to the cpuset.cpus value when the cpuset becomes
a valid partition root.
When cpuset.cpus is being cleared by the user, effective_xcpus should
only be cleared when cpuset.cpus.exclusive is not set. However, that
is not currently the case.
# cd /sys/fs/cgroup/
# mkdir test
# echo +cpuset > cgroup.subtree_control
# cd test
# echo 3 > cpuset.cpus.exclusive
# cat cpuset.cpus.exclusive.effective
3
# echo > cpuset.cpus
# cat cpuset.cpus.exclusive.effective // was cleared
Fix it by clearing effective_xcpus only if cpuset.cpus.exclusive is
not set.
Fixes: e2ffe502ba45 ("cgroup/cpuset: Add cpuset.cpus.exclusive for v2")
Reported-by: Chen Ridong <chenridong@...wei.com>
Signed-off-by: Waiman Long <longman@...hat.com>
---
kernel/cgroup/cpuset.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index f1846a08e245..7287cecb27d1 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -2508,7 +2508,8 @@ static int update_cpumask(struct cpuset *cs, struct cpuset *trialcs,
*/
if (!*buf) {
cpumask_clear(trialcs->cpus_allowed);
- cpumask_clear(trialcs->effective_xcpus);
+ if (cpumask_empty(trialcs->exclusive_cpus))
+ cpumask_clear(trialcs->effective_xcpus);
} else {
retval = cpulist_parse(buf, trialcs->cpus_allowed);
if (retval < 0)
--
2.43.5
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