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Subject[PATCH 12/13] sched, deadline: Fixup the smp-affinity mask tests
For now deadline tasks are not allowed to set smp affinity; however
the current tests are wrong, cure this.

The test in __sched_setscheduler() also uses an on-stack cpumask_t
which is a no-no.

Change both tests to use cpumask_subset() such that we test the root
domain span to be a subset of the cpus_allowed mask. This way we're
sure the tasks can always run on all CPUs they can be balanced over,
and have no effective affinity constraints.

Signed-off-by: Peter Zijlstra <peterz@infradead.org>
---
kernel/sched/core.c | 44 +++++++++---------------------------
kernel/sched/rt.c | 62 +++++++++++++++++++++++++++++++++++++--------------
kernel/sched/sched.h | 2 +
3 files changed, 58 insertions(+), 50 deletions(-)

--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -3384,23 +3384,14 @@ static int __sched_setscheduler(struct t
#ifdef CONFIG_SMP
if (dl_bandwidth_enabled() && dl_policy(policy)) {
cpumask_t *span = rq->rd->span;
- cpumask_t act_affinity;
-
- /*
- * cpus_allowed mask is statically initialized with
- * CPU_MASK_ALL, span is instead dynamic. Here we
- * compute the "dynamic" affinity of a task.
- */
- cpumask_and(&act_affinity, &p->cpus_allowed,
- cpu_active_mask);

/*
* Don't allow tasks with an affinity mask smaller than
* the entire root_domain to become SCHED_DEADLINE. We
* will also fail if there's no bandwidth available.
*/
- if (!cpumask_equal(&act_affinity, span) ||
- rq->rd->dl_bw.bw == 0) {
+ if (!cpumask_subset(span, &p->cpus_allowed) ||
+ rq->rd->dl_bw.bw == 0) {
__task_rq_unlock(rq);
raw_spin_unlock_irqrestore(&p->pi_lock, flags);
return -EPERM;
@@ -3421,8 +3412,7 @@ static int __sched_setscheduler(struct t
* of a SCHED_DEADLINE task) we need to check if enough bandwidth
* is available.
*/
- if ((dl_policy(policy) || dl_task(p)) &&
- dl_overflow(p, policy, attr)) {
+ if ((dl_policy(policy) || dl_task(p)) && dl_overflow(p, policy, attr)) {
task_rq_unlock(rq, p, &flags);
return -EBUSY;
}
@@ -3861,6 +3851,10 @@ long sched_setaffinity(pid_t pid, const
if (retval)
goto out_unlock;

+
+ cpuset_cpus_allowed(p, cpus_allowed);
+ cpumask_and(new_mask, in_mask, cpus_allowed);
+
/*
* Since bandwidth control happens on root_domain basis,
* if admission test is enabled, we only admit -deadline
@@ -3871,16 +3865,12 @@ long sched_setaffinity(pid_t pid, const
if (task_has_dl_policy(p)) {
const struct cpumask *span = task_rq(p)->rd->span;

- if (dl_bandwidth_enabled() &&
- !cpumask_equal(in_mask, span)) {
+ if (dl_bandwidth_enabled() && !cpumask_subset(span, new_mask)) {
retval = -EBUSY;
goto out_unlock;
}
}
#endif
-
- cpuset_cpus_allowed(p, cpus_allowed);
- cpumask_and(new_mask, in_mask, cpus_allowed);
again:
retval = set_cpus_allowed_ptr(p, new_mask);

@@ -4536,7 +4526,7 @@ EXPORT_SYMBOL_GPL(set_cpus_allowed_ptr);
* When dealing with a -deadline task, we have to check if moving it to
* a new CPU is possible or not. In fact, this is only true iff there
* is enough bandwidth available on such CPU, otherwise we want the
- * whole migration progedure to fail over.
+ * whole migration procedure to fail over.
*/
static inline
bool set_task_cpu_dl(struct task_struct *p, unsigned int cpu)



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