From: luca abeni <luca.abeni@santannapisa.it>
Update sched_group_rt_runtime/period and sched_group_set_rt_runtime/period
to use the newly defined data structures and perform necessary checks to
update both the runtime and period of a given group.
The set functions call tg_set_rt_bandwidth() which is also updated:
- Use the newly added HCBS dl_bandwidth structure instead of rt_bandwidth.
- Update __rt_schedulable() to check for numerical issues:
- Prevent a non-zero runtime that is too small, since a non-zero very
small runtime will make the servers behave as they had zero runtime.
- Since some computation use signed integers, the period might be so
big that when read as a signed integer becomes a negative number, and
we don't want that. If the period satisfies this prerequisite, also
the runtime will do, since the runtime is always less than or equal
to the period.
- Update tg_rt_schedulable(), used when walking the cgroup tree to check
if all invariants are met:
- Update most of the instructions to obtain data from the newly added
data structures (dl_bandwidth).
- If the task group is the root group, run a total bandwidth check with
the newly added dl_check_tg() function.
- After all checks are successful, if the changed group is not the root
cgroup, update the assigned runtime and period to all the local
deadline servers.
- Additionally use a mutex guard instead of manually locking/unlocking.
Add dl_check_tg(), which performs an admission control test similar to
__dl_overflow, but this time we are updating the cgroup's total bandwidth
rather than scheduling a new DEADLINE task or updating a non-cgroup
deadline server.
Finally, prevent creation of a cgroup hierarchy with depth greater than
two, as this will be addressed in a future patch. A depth two hierarchy
is sufficient for now for testing the patchset.
Co-developed-by: Alessio Balsini <a.balsini@sssup.it>
Signed-off-by: Alessio Balsini <a.balsini@sssup.it>
Co-developed-by: Andrea Parri <parri.andrea@gmail.com>
Signed-off-by: Andrea Parri <parri.andrea@gmail.com>
Co-developed-by: Yuri Andriaccio <yurand2000@gmail.com>
Signed-off-by: Yuri Andriaccio <yurand2000@gmail.com>
Signed-off-by: luca abeni <luca.abeni@santannapisa.it>
---
kernel/sched/core.c | 6 ++++
kernel/sched/deadline.c | 46 +++++++++++++++++++++++----
kernel/sched/rt.c | 70 +++++++++++++++++++++++------------------
kernel/sched/sched.h | 1 +
4 files changed, 87 insertions(+), 36 deletions(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index d7fc83cdae..bdf1bebe52 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -9253,6 +9253,12 @@ cpu_cgroup_css_alloc(struct cgroup_subsys_state *parent_css)
return &root_task_group.css;
}
+ /* Do not allow cpu_cgroup hierachies with depth greater than 2. */
+#ifdef CONFIG_RT_GROUP_SCHED
+ if (parent != &root_task_group)
+ return ERR_PTR(-EINVAL);
+#endif
+
tg = sched_create_group(parent);
if (IS_ERR(tg))
return ERR_PTR(-ENOMEM);
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index b890fdd4b2..7ed157dfa6 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -347,7 +347,47 @@ void cancel_inactive_timer(struct sched_dl_entity *dl_se)
cancel_dl_timer(dl_se, &dl_se->inactive_timer);
}
+/*
+ * Used for dl_bw check and update, used under sched_rt_handler()::mutex and
+ * sched_domains_mutex.
+ */
+u64 dl_cookie;
+
#ifdef CONFIG_RT_GROUP_SCHED
+int dl_check_tg(unsigned long total)
+{
+ unsigned long flags;
+ int which_cpu;
+ int cap;
+ struct dl_bw *dl_b;
+ u64 gen = ++dl_cookie;
+
+ for_each_possible_cpu(which_cpu) {
+ rcu_read_lock_sched();
+
+ if (!dl_bw_visited(which_cpu, gen)) {
+ cap = dl_bw_capacity(which_cpu);
+ dl_b = dl_bw_of(which_cpu);
+
+ raw_spin_lock_irqsave(&dl_b->lock, flags);
+
+ if (dl_b->bw != -1 &&
+ cap_scale(dl_b->bw, cap) < dl_b->total_bw + cap_scale(total, cap)) {
+ raw_spin_unlock_irqrestore(&dl_b->lock, flags);
+ rcu_read_unlock_sched();
+
+ return 0;
+ }
+
+ raw_spin_unlock_irqrestore(&dl_b->lock, flags);
+ }
+
+ rcu_read_unlock_sched();
+ }
+
+ return 1;
+}
+
void dl_init_tg(struct sched_dl_entity *dl_se, u64 rt_runtime, u64 rt_period)
{
struct rq *rq = container_of(dl_se->dl_rq, struct rq, dl);
@@ -3150,12 +3190,6 @@ DEFINE_SCHED_CLASS(dl) = {
#endif
};
-/*
- * Used for dl_bw check and update, used under sched_rt_handler()::mutex and
- * sched_domains_mutex.
- */
-u64 dl_cookie;
-
int sched_dl_global_validate(void)
{
u64 runtime = global_rt_runtime();
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index 2b7c4b7754..b0a6da20b5 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -2007,11 +2007,6 @@ DEFINE_SCHED_CLASS(rt) = {
};
#ifdef CONFIG_RT_GROUP_SCHED
-/*
- * Ensure that the real time constraints are schedulable.
- */
-static DEFINE_MUTEX(rt_constraints_mutex);
-
static inline int tg_has_rt_tasks(struct task_group *tg)
{
struct task_struct *task;
@@ -2045,8 +2040,8 @@ static int tg_rt_schedulable(struct task_group *tg, void *data)
unsigned long total, sum = 0;
u64 period, runtime;
- period = ktime_to_ns(tg->rt_bandwidth.rt_period);
- runtime = tg->rt_bandwidth.rt_runtime;
+ period = tg->dl_bandwidth.dl_period;
+ runtime = tg->dl_bandwidth.dl_runtime;
if (tg == d->tg) {
period = d->rt_period;
@@ -2062,8 +2057,7 @@ static int tg_rt_schedulable(struct task_group *tg, void *data)
/*
* Ensure we don't starve existing RT tasks if runtime turns zero.
*/
- if (rt_bandwidth_enabled() && !runtime &&
- tg->rt_bandwidth.rt_runtime && tg_has_rt_tasks(tg))
+ if (dl_bandwidth_enabled() && !runtime && tg_has_rt_tasks(tg))
return -EBUSY;
if (WARN_ON(!rt_group_sched_enabled() && tg != &root_task_group))
@@ -2077,12 +2071,17 @@ static int tg_rt_schedulable(struct task_group *tg, void *data)
if (total > to_ratio(global_rt_period(), global_rt_runtime()))
return -EINVAL;
+ if (tg == &root_task_group) {
+ if (!dl_check_tg(total))
+ return -EBUSY;
+ }
+
/*
* The sum of our children's runtime should not exceed our own.
*/
list_for_each_entry_rcu(child, &tg->children, siblings) {
- period = ktime_to_ns(child->rt_bandwidth.rt_period);
- runtime = child->rt_bandwidth.rt_runtime;
+ period = child->dl_bandwidth.dl_period;
+ runtime = child->dl_bandwidth.dl_runtime;
if (child == d->tg) {
period = d->rt_period;
@@ -2108,6 +2107,20 @@ static int __rt_schedulable(struct task_group *tg, u64 period, u64 runtime)
.rt_runtime = runtime,
};
+ /*
+ * Since we truncate DL_SCALE bits, make sure we're at least
+ * that big.
+ */
+ if (runtime != 0 && runtime < (1ULL << DL_SCALE))
+ return -EINVAL;
+
+ /*
+ * Since we use the MSB for wrap-around and sign issues, make
+ * sure it's not set (mind that period can be equal to zero).
+ */
+ if (period & (1ULL << 63))
+ return -EINVAL;
+
rcu_read_lock();
ret = walk_tg_tree(tg_rt_schedulable, tg_nop, &data);
rcu_read_unlock();
@@ -2118,6 +2131,7 @@ static int __rt_schedulable(struct task_group *tg, u64 period, u64 runtime)
static int tg_set_rt_bandwidth(struct task_group *tg,
u64 rt_period, u64 rt_runtime)
{
+ static DEFINE_MUTEX(rt_constraints_mutex);
int i, err = 0;
/*
@@ -2137,34 +2151,30 @@ static int tg_set_rt_bandwidth(struct task_group *tg,
if (rt_runtime != RUNTIME_INF && rt_runtime > max_rt_runtime)
return -EINVAL;
- mutex_lock(&rt_constraints_mutex);
+ guard(mutex)(&rt_constraints_mutex);
err = __rt_schedulable(tg, rt_period, rt_runtime);
if (err)
- goto unlock;
+ return err;
- raw_spin_lock_irq(&tg->rt_bandwidth.rt_runtime_lock);
- tg->rt_bandwidth.rt_period = ns_to_ktime(rt_period);
- tg->rt_bandwidth.rt_runtime = rt_runtime;
+ guard(raw_spinlock_irq)(&tg->dl_bandwidth.dl_runtime_lock);
+ tg->dl_bandwidth.dl_period = rt_period;
+ tg->dl_bandwidth.dl_runtime = rt_runtime;
- for_each_possible_cpu(i) {
- struct rt_rq *rt_rq = tg->rt_rq[i];
+ if (tg == &root_task_group)
+ return 0;
- raw_spin_lock(&rt_rq->rt_runtime_lock);
- rt_rq->rt_runtime = rt_runtime;
- raw_spin_unlock(&rt_rq->rt_runtime_lock);
+ for_each_possible_cpu(i) {
+ dl_init_tg(tg->dl_se[i], rt_runtime, rt_period);
}
- raw_spin_unlock_irq(&tg->rt_bandwidth.rt_runtime_lock);
-unlock:
- mutex_unlock(&rt_constraints_mutex);
- return err;
+ return 0;
}
int sched_group_set_rt_runtime(struct task_group *tg, long rt_runtime_us)
{
u64 rt_runtime, rt_period;
- rt_period = ktime_to_ns(tg->rt_bandwidth.rt_period);
+ rt_period = tg->dl_bandwidth.dl_period;
rt_runtime = (u64)rt_runtime_us * NSEC_PER_USEC;
if (rt_runtime_us < 0)
rt_runtime = RUNTIME_INF;
@@ -2178,10 +2188,10 @@ long sched_group_rt_runtime(struct task_group *tg)
{
u64 rt_runtime_us;
- if (tg->rt_bandwidth.rt_runtime == RUNTIME_INF)
+ if (tg->dl_bandwidth.dl_runtime == RUNTIME_INF)
return -1;
- rt_runtime_us = tg->rt_bandwidth.rt_runtime;
+ rt_runtime_us = tg->dl_bandwidth.dl_runtime;
do_div(rt_runtime_us, NSEC_PER_USEC);
return rt_runtime_us;
}
@@ -2194,7 +2204,7 @@ int sched_group_set_rt_period(struct task_group *tg, u64 rt_period_us)
return -EINVAL;
rt_period = rt_period_us * NSEC_PER_USEC;
- rt_runtime = tg->rt_bandwidth.rt_runtime;
+ rt_runtime = tg->dl_bandwidth.dl_runtime;
return tg_set_rt_bandwidth(tg, rt_period, rt_runtime);
}
@@ -2203,7 +2213,7 @@ long sched_group_rt_period(struct task_group *tg)
{
u64 rt_period_us;
- rt_period_us = ktime_to_ns(tg->rt_bandwidth.rt_period);
+ rt_period_us = tg->dl_bandwidth.dl_period;
do_div(rt_period_us, NSEC_PER_USEC);
return rt_period_us;
}
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index bc3ed02e40..334ab6d597 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -419,6 +419,7 @@ extern void dl_server_init(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq,
struct rq *served_rq,
dl_server_pick_f pick_task);
extern void sched_init_dl_servers(void);
+extern int dl_check_tg(unsigned long total);
extern void dl_init_tg(struct sched_dl_entity *dl_se, u64 rt_runtime, u64 rt_period);
extern void dl_server_update_idle_time(struct rq *rq,
--
2.51.0