Commit 234b8ab6 authored by Will Deacon's avatar Will Deacon Committed by Peter Zijlstra
Browse files

sched: Introduce dl_task_check_affinity() to check proposed affinity 



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

Signed-off-by: default avatarWill Deacon <will@kernel.org>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: default avatarDaniel Bristot de Oliveira <bristot@redhat.com>
Link: https://lore.kernel.org/r/20210730112443.23245-10-will@kernel.org
parent 07ec77a1

include/linux/sched.h

+6 −0
Original line number Diff line number Diff line
@@ -1709,6 +1709,7 @@ 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 int dl_task_check_affinity(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
@@ -1731,6 +1732,11 @@ static inline void release_user_cpus_ptr(struct task_struct *p) 
{

	WARN_ON(p->user_cpus_ptr);

}



static inline int dl_task_check_affinity(struct task_struct *p, const struct cpumask *mask)

{

	return 0;

}

#endif



extern int yield_to(struct task_struct *p, bool preempt);

kernel/sched/core.c

+29 −17
Original line number Diff line number Diff line
@@ -7756,6 +7756,32 @@ SYSCALL_DEFINE4(sched_getattr, pid_t, pid, struct sched_attr __user *, uattr, 
	return retval;

}



#ifdef CONFIG_SMP

int dl_task_check_affinity(struct task_struct *p, const struct cpumask *mask)

{

	int ret = 0;



	/*

	 * If the task isn't a deadline task or admission control is

	 * disabled then we don't care about affinity changes.

	 */

	if (!task_has_dl_policy(p) || !dl_bandwidth_enabled())

		return 0;



	/*

	 * Since bandwidth control happens on root_domain basis,

	 * if admission test is enabled, we only admit -deadline

	 * tasks allowed to run on all the CPUs in the task's

	 * root_domain.

	 */

	rcu_read_lock();

	if (!cpumask_subset(task_rq(p)->rd->span, mask))

		ret = -EBUSY;

	rcu_read_unlock();

	return ret;

}

#endif



static int

__sched_setaffinity(struct task_struct *p, const struct cpumask *mask)

{
@@ -7773,23 +7799,9 @@ __sched_setaffinity(struct task_struct *p, const struct cpumask *mask) 
	cpuset_cpus_allowed(p, cpus_allowed);

	cpumask_and(new_mask, mask, cpus_allowed);



	/*

	 * Since bandwidth control happens on root_domain basis,

	 * if admission test is enabled, we only admit -deadline

	 * tasks allowed to run on all the CPUs in the task's

	 * root_domain.

	 */

#ifdef CONFIG_SMP

	if (task_has_dl_policy(p) && dl_bandwidth_enabled()) {

		rcu_read_lock();

		if (!cpumask_subset(task_rq(p)->rd->span, new_mask)) {

			retval = -EBUSY;

			rcu_read_unlock();

	retval = dl_task_check_affinity(p, new_mask);

	if (retval)

		goto out_free_new_mask;

		}

		rcu_read_unlock();

	}

#endif

again:

	retval = __set_cpus_allowed_ptr(p, new_mask, SCA_CHECK | SCA_USER);

	if (retval)