sched: fix warning in sched_setaffinity

mainline inclusion
from mainline-6.13-rc3
commit 70ee7947a29029736a1a06c73a48ff37674a851b
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/IBD13G

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git/commit/?id=70ee7947a29029736a1a06c73a48ff37674a851b



--------------------------------

Commit 8f9ea86f added some logic to sched_setaffinity that included
a WARN when a per-task affinity assignment races with a cpuset update.

Specifically, we can have a race where a cpuset update results in the
task affinity no longer being a subset of the cpuset. That's fine; we
have a fallback to instead use the cpuset mask. However, we have a WARN
set up that will trigger if the cpuset mask has no overlap at all with
the requested task affinity. This shouldn't be a warning condition; its
trivial to create this condition.

Reproduced the warning by the following setup:

- $PID inside a cpuset cgroup
- another thread repeatedly switching the cpuset cpus from 1-2 to just 1
- another thread repeatedly setting the $PID affinity (via taskset) to 2

Fixes: 8f9ea86f ("sched: Always preserve the user requested cpumask")
Signed-off-by: Josh Don <joshdon@google.com>
Acked-and-tested-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Waiman Long <longman@redhat.com>
Tested-by: Madadi Vineeth Reddy <vineethr@linux.ibm.com>
Link: https://lkml.kernel.org/r/20241111182738.1832953-1-joshdon@google.com


Conflicts:
	kernel/sched/core.c
	kernel/sched/syscalls.c
[The linux stable 6.6 lacks this commit 70ee7947a290 ("sched: fix
warning in sched_setaffinity"), so pick from linux mainline, this
function "__sched_setaffinity" has been moved from core to syscall in
mainline.]
Signed-off-by: Zicheng Qu <quzicheng@huawei.com>