[PATCH v5 07/15] cpuset: Don't use the cpu_possible_mask as a last resort for cgroup v1

Will Deacon will at kernel.org
Tue Dec 8 08:28:27 EST 2020

If the scheduler cannot find an allowed CPU for a task,
cpuset_cpus_allowed_fallback() will widen the affinity to cpu_possible_mask
if cgroup v1 is in use.

In preparation for allowing architectures to provide their own fallback
mask, just return early if we're not using cgroup v2 and allow
select_fallback_rq() to figure out the mask by itself.

Cc: Li Zefan <lizefan at huawei.com>
Cc: Tejun Heo <tj at kernel.org>
Cc: Johannes Weiner <hannes at cmpxchg.org>
Reviewed-by: Quentin Perret <qperret at google.com>
Signed-off-by: Will Deacon <will at kernel.org>
 kernel/cgroup/cpuset.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index 57b5b5d0a5fd..e970737c3ed2 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -3299,9 +3299,11 @@ void cpuset_cpus_allowed(struct task_struct *tsk, struct cpumask *pmask)
 void cpuset_cpus_allowed_fallback(struct task_struct *tsk)
+	if (!is_in_v2_mode())
+		return; /* select_fallback_rq will try harder */
-	do_set_cpus_allowed(tsk, is_in_v2_mode() ?
-		task_cs(tsk)->cpus_allowed : cpu_possible_mask);
+	do_set_cpus_allowed(tsk, task_cs(tsk)->cpus_allowed);

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