Re: [PATCH v8 12/19] sched: Introduce task_cpus_dl_admissible() to check proposed affinity

In preparation for restricting the affinity of a task during execve()
on arm64, introduce a new task_cpus_dl_admissible() helper function to
give an indication as to whether the restricted mask is admissible for
a deadline task.

Signed-off-by: Will Deacon <will@kernel.org>
---
 include/linux/sched.h |  6 ++++++
 kernel/sched/core.c   | 44 +++++++++++++++++++++++++++----------------
 2 files changed, 34 insertions(+), 16 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 91a6cfeae242..9b17d8cfa6ef 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h

@@ -1691,6 +1691,7 @@ extern void do_set_cpus_allowed(struct task_struct *p, const struct cpumask *new
 extern int set_cpus_allowed_ptr(struct task_struct *p, const struct cpumask *new_mask);
 extern int dup_user_cpus_ptr(struct task_struct *dst, struct task_struct *src, int node);
 extern void release_user_cpus_ptr(struct task_struct *p);
+extern bool task_cpus_dl_admissible(struct task_struct *p, const struct cpumask *mask);
 extern void force_compatible_cpus_allowed_ptr(struct task_struct *p);
 extern void relax_compatible_cpus_allowed_ptr(struct task_struct *p);
 #else

@@ -1713,6 +1714,11 @@ static inline void release_user_cpus_ptr(struct task_struct *p)
 {
 	WARN_ON(p->user_cpus_ptr);
 }
+
+static inline bool task_cpus_dl_admissible(struct task_struct *p, const struct cpumask *mask)
+{
+	return true;
+}
 #endif
 
 extern int yield_to(struct task_struct *p, bool preempt);

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 58e2cf7520c0..b4f8dc18ae11 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c

@@ -6933,6 +6933,31 @@ SYSCALL_DEFINE4(sched_getattr, pid_t, pid, struct sched_attr __user *, uattr,
 	return retval;
 }
 
+#ifdef CONFIG_SMP
+bool task_cpus_dl_admissible(struct task_struct *p, const struct cpumask *mask)