From: Josh Don joshdon@google.com

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=70ee7...

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Commit 8f9ea86fdf99b 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: 8f9ea86fdf99b ("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 iConflicts: 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 --- kernel/sched/core.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 7a9aff1dbb3c..5569c89bbaf3 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -8415,7 +8415,7 @@ __sched_setaffinity(struct task_struct *p, struct affinity_context *ctx) bool empty = !cpumask_and(new_mask, new_mask, ctx->user_mask);

- if (WARN_ON_ONCE(empty)) + if (empty) cpumask_copy(new_mask, cpus_allowed); } __set_cpus_allowed_ptr(p, ctx);