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FROMLIST: cpuset: Don't use the cpu_possible_mask as a last resort for cgroup v1

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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@huawei.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Quentin Perret <qperret@google.com>
Signed-off-by: Will Deacon <will@kernel.org>
[will: Check task_cpu_possible_mask() in v2 mode as per on-list comments]
Link: https://lore.kernel.org/r/20201217121552.ds7g2icvqp5nvtha@e107158-lin.cambridge.arm.com
Bug: 178507149
Link: https://lore.kernel.org/linux-arch/20201208132835.6151-8-will@kernel.org/
Signed-off-by: Will Deacon <willdeacon@google.com>
Change-Id: I7a6b234c28495bae6feeecceafb841aae4de6046
This commit is contained in:
Will Deacon
2020-11-10 18:21:28 +00:00
committed by Will Deacon
parent 1a96879cb3
commit 210463b39c
1 changed files with 7 additions and 2 deletions
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9
kernel/cgroup/cpuset.c
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@@ -3336,9 +3336,14 @@ void cpuset_cpus_allowed(struct task_struct *tsk, struct cpumask *pmask)
void cpuset_cpus_allowed_fallback(struct task_struct *tsk)
{
const struct cpumask *cs_mask = task_cs(tsk)->cpus_allowed;
const struct cpumask *possible_mask = task_cpu_possible_mask(tsk);
if (!is_in_v2_mode() || !cpumask_subset(cs_mask, possible_mask))
return; /* select_fallback_rq will try harder */
rcu_read_lock();
do_set_cpus_allowed(tsk, is_in_v2_mode() ?
task_cs(tsk)->cpus_allowed : cpu_possible_mask);
do_set_cpus_allowed(tsk, cs_mask);
rcu_read_unlock();
/*