[PATCH 5.10 429/545] sched/deadline: Merge dl_task_can_attach() and dl_cpu_busy()

Greg Kroah-Hartman
2022-08-19T16:38:27Z

From: Dietmar Eggemann <dietmar.eggemann@arm.com>

[ Upstream commit 772b6539fdda31462cc08368e78df60b31a58bab ]

Both functions are doing almost the same, that is checking if admission
control is still respected.

With exclusive cpusets, dl_task_can_attach() checks if the destination
cpuset (i.e. its root domain) has enough CPU capacity to accommodate the
task.
dl_cpu_busy() checks if there is enough CPU capacity in the cpuset in
case the CPU is hot-plugged out.

dl_task_can_attach() is used to check if a task can be admitted while
dl_cpu_busy() is used to check if a CPU can be hotplugged out.

Make dl_cpu_busy() able to deal with a task and use it instead of
dl_task_can_attach() in task_can_attach().

Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Juri Lelli <juri.lelli@redhat.com>
Link: https://lore.kernel.org/r/20220302183433.333029-4-dietmar.eggemann@arm.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
kernel/sched/core.c | 13 +++++++----
kernel/sched/deadline.c | 52 +++++++++++------------------------------
kernel/sched/sched.h | 3 +--
3 files changed, 24 insertions(+), 44 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index e437d946b27b..042efabf5378 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -6605,8 +6605,11 @@ int task_can_attach(struct task_struct *p,
}

if (dl_task(p) && !cpumask_intersects(task_rq(p)->rd->span,
- cs_cpus_allowed))
- ret = dl_task_can_attach(p, cs_cpus_allowed);
+ cs_cpus_allowed)) {
+ int cpu = cpumask_any_and(cpu_active_mask, cs_cpus_allowed);
+
+ ret = dl_cpu_busy(cpu, p);
+ }

out:
return ret;
@@ -6865,8 +6868,10 @@ static void cpuset_cpu_active(void)
static int cpuset_cpu_inactive(unsigned int cpu)
{
if (!cpuhp_tasks_frozen) {
- if (dl_cpu_busy(cpu))
- return -EBUSY;
+ int ret = dl_cpu_busy(cpu, NULL);
+
+ if (ret)
+ return ret;
cpuset_update_active_cpus();
} else {
num_cpus_frozen++;
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 933706106b98..aaf98771f935 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -2825,41 +2825,6 @@ bool dl_param_changed(struct task_struct *p, const struct sched_attr *attr)
}

#ifdef CONFIG_SMP
-int dl_task_can_attach(struct task_struct *p, const struct cpumask *cs_cpus_allowed)
-{
- unsigned long flags, cap;
- unsigned int dest_cpu;
- struct dl_bw *dl_b;
- bool overflow;
- int ret;
-
- dest_cpu = cpumask_any_and(cpu_active_mask, cs_cpus_allowed);
-
- rcu_read_lock_sched();
- dl_b = dl_bw_of(dest_cpu);
- raw_spin_lock_irqsave(&dl_b->lock, flags);
- cap = dl_bw_capacity(dest_cpu);
- overflow = __dl_overflow(dl_b, cap, 0, p->dl.dl_bw);
- if (overflow) {
- ret = -EBUSY;
- } else {
- /*
- * We reserve space for this task in the destination
- * root_domain, as we can't fail after this point.
- * We will free resources in the source root_domain
- * later on (see set_cpus_allowed_dl()).
- */
- int cpus = dl_bw_cpus(dest_cpu);
-
- __dl_add(dl_b, p->dl.dl_bw, cpus);
- ret = 0;
- }
- raw_spin_unlock_irqrestore(&dl_b->lock, flags);
- rcu_read_unlock_sched();
-
- return ret;
-}
-
int dl_cpuset_cpumask_can_shrink(const struct cpumask *cur,
const struct cpumask *trial)
{
@@ -2881,7 +2846,7 @@ int dl_cpuset_cpumask_can_shrink(const struct cpumask *cur,
return ret;
}

-bool dl_cpu_busy(unsigned int cpu)
+int dl_cpu_busy(int cpu, struct task_struct *p)
{
unsigned long flags, cap;
struct dl_bw *dl_b;
@@ -2891,11 +2856,22 @@ bool dl_cpu_busy(unsigned int cpu)
dl_b = dl_bw_of(cpu);
raw_spin_lock_irqsave(&dl_b->lock, flags);
cap = dl_bw_capacity(cpu);
- overflow = __dl_overflow(dl_b, cap, 0, 0);
+ overflow = __dl_overflow(dl_b, cap, 0, p ? p->dl.dl_bw : 0);
+
+ if (!overflow && p) {
+ /*
+ * We reserve space for this task in the destination
+ * root_domain, as we can't fail after this point.
+ * We will free resources in the source root_domain
+ * later on (see set_cpus_allowed_dl()).
+ */
+ __dl_add(dl_b, p->dl.dl_bw, dl_bw_cpus(cpu));
+ }
+
raw_spin_unlock_irqrestore(&dl_b->lock, flags);
rcu_read_unlock_sched();

- return overflow;
+ return overflow ? -EBUSY : 0;
}
#endif

diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 8d39f5d99172..12c65628801c 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -347,9 +347,8 @@ extern void __setparam_dl(struct task_struct *p, const struct sched_attr *attr);
extern void __getparam_dl(struct task_struct *p, struct sched_attr *attr);
extern bool __checkparam_dl(const struct sched_attr *attr);
extern bool dl_param_changed(struct task_struct *p, const struct sched_attr *attr);
-extern int dl_task_can_attach(struct task_struct *p, const struct cpumask *cs_cpus_allowed);
extern int dl_cpuset_cpumask_can_shrink(const struct cpumask *cur, const struct cpumask *trial);
-extern bool dl_cpu_busy(unsigned int cpu);
+extern int dl_cpu_busy(int cpu, struct task_struct *p);

#ifdef CONFIG_CGROUP_SCHED

--
2.35.1