[PATCH 09/39] sched: Add @reason to sched_class->rq_{on|off}line()

Tejun Heo
2024-05-01T15:13:34Z

->rq_{on|off}line are called either during CPU hotplug or cpuset partition
updates. A planned BPF extensible sched_class wants to tell the BPF
scheduler progs about CPU hotplug events in a way that's synchronized with
rq state changes.

As the BPF scheduler progs aren't necessarily affected by cpuset partition
updates, we need a way to distinguish the two types of events. Let's add an
argument to tell them apart.

v2: Patch description updated to detail the expected use.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: David Vernet <dvernet@meta.com>
Acked-by: Josh Don <joshdon@google.com>
Acked-by: Hao Luo <haoluo@google.com>
Acked-by: Barret Rhoden <brho@google.com>
---
kernel/sched/core.c | 12 ++++++------
kernel/sched/deadline.c | 4 ++--
kernel/sched/fair.c | 4 ++--
kernel/sched/rt.c | 4 ++--
kernel/sched/sched.h | 13 +++++++++----
kernel/sched/topology.c | 4 ++--
6 files changed, 23 insertions(+), 18 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index e48af9fbbd71..90b505fbb488 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -9593,7 +9593,7 @@ static inline void balance_hotplug_wait(void)

#endif /* CONFIG_HOTPLUG_CPU */

-void set_rq_online(struct rq *rq)
+void set_rq_online(struct rq *rq, enum rq_onoff_reason reason)
{
if (!rq->online) {
const struct sched_class *class;
@@ -9603,12 +9603,12 @@ void set_rq_online(struct rq *rq)

for_each_class(class) {
if (class->rq_online)
- class->rq_online(rq);
+ class->rq_online(rq, reason);
}
}
}

-void set_rq_offline(struct rq *rq)
+void set_rq_offline(struct rq *rq, enum rq_onoff_reason reason)
{
if (rq->online) {
const struct sched_class *class;
@@ -9616,7 +9616,7 @@ void set_rq_offline(struct rq *rq)
update_rq_clock(rq);
for_each_class(class) {
if (class->rq_offline)
- class->rq_offline(rq);
+ class->rq_offline(rq, reason);
}

cpumask_clear_cpu(rq->cpu, rq->rd->online);
@@ -9712,7 +9712,7 @@ int sched_cpu_activate(unsigned int cpu)
rq_lock_irqsave(rq, &rf);
if (rq->rd) {
BUG_ON(!cpumask_test_cpu(cpu, rq->rd->span));
- set_rq_online(rq);
+ set_rq_online(rq, RQ_ONOFF_HOTPLUG);
}
rq_unlock_irqrestore(rq, &rf);

@@ -9756,7 +9756,7 @@ int sched_cpu_deactivate(unsigned int cpu)
rq_lock_irqsave(rq, &rf);
if (rq->rd) {
BUG_ON(!cpumask_test_cpu(cpu, rq->rd->span));
- set_rq_offline(rq);
+ set_rq_offline(rq, RQ_ONOFF_HOTPLUG);
}
rq_unlock_irqrestore(rq, &rf);

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index a04a436af8cc..010d1dc5f918 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -2607,7 +2607,7 @@ static void set_cpus_allowed_dl(struct task_struct *p,
}

/* Assumes rq->lock is held */
-static void rq_online_dl(struct rq *rq)
+static void rq_online_dl(struct rq *rq, enum rq_onoff_reason reason)
{
if (rq->dl.overloaded)
dl_set_overload(rq);
@@ -2618,7 +2618,7 @@ static void rq_online_dl(struct rq *rq)
}

/* Assumes rq->lock is held */
-static void rq_offline_dl(struct rq *rq)
+static void rq_offline_dl(struct rq *rq, enum rq_onoff_reason reason)
{
if (rq->dl.overloaded)
dl_clear_overload(rq);
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 5d7cffee1a4e..8032256d3972 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -12446,14 +12446,14 @@ void trigger_load_balance(struct rq *rq)
nohz_balancer_kick(rq);
}

-static void rq_online_fair(struct rq *rq)
+static void rq_online_fair(struct rq *rq, enum rq_onoff_reason reason)
{
update_sysctl();

update_runtime_enabled(rq);
}

-static void rq_offline_fair(struct rq *rq)
+static void rq_offline_fair(struct rq *rq, enum rq_onoff_reason reason)
{
update_sysctl();

diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index 3261b067b67e..8620474d117d 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -2426,7 +2426,7 @@ static void task_woken_rt(struct rq *rq, struct task_struct *p)
}

/* Assumes rq->lock is held */
-static void rq_online_rt(struct rq *rq)
+static void rq_online_rt(struct rq *rq, enum rq_onoff_reason reason)
{
if (rq->rt.overloaded)
rt_set_overload(rq);
@@ -2437,7 +2437,7 @@ static void rq_online_rt(struct rq *rq)
}

/* Assumes rq->lock is held */
-static void rq_offline_rt(struct rq *rq)
+static void rq_offline_rt(struct rq *rq, enum rq_onoff_reason reason)
{
if (rq->rt.overloaded)
rt_clear_overload(rq);
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 0b6a34ba2457..bcc8056acadb 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -2271,6 +2271,11 @@ extern const u32 sched_prio_to_wmult[40];

#define RETRY_TASK ((void *)-1UL)

+enum rq_onoff_reason {
+ RQ_ONOFF_HOTPLUG, /* CPU is going on/offline */
+ RQ_ONOFF_TOPOLOGY, /* sched domain topology update */
+};
+
struct affinity_context {
const struct cpumask *new_mask;
struct cpumask *user_mask;
@@ -2309,8 +2314,8 @@ struct sched_class {

void (*set_cpus_allowed)(struct task_struct *p, struct affinity_context *ctx);

- void (*rq_online)(struct rq *rq);
- void (*rq_offline)(struct rq *rq);
+ void (*rq_online)(struct rq *rq, enum rq_onoff_reason reason);
+ void (*rq_offline)(struct rq *rq, enum rq_onoff_reason reason);

struct rq *(*find_lock_rq)(struct task_struct *p, struct rq *rq);
#endif
@@ -2853,8 +2858,8 @@ static inline void double_rq_unlock(struct rq *rq1, struct rq *rq2)
raw_spin_rq_unlock(rq1);
}

-extern void set_rq_online (struct rq *rq);
-extern void set_rq_offline(struct rq *rq);
+extern void set_rq_online (struct rq *rq, enum rq_onoff_reason reason);
+extern void set_rq_offline(struct rq *rq, enum rq_onoff_reason reason);
extern bool sched_smp_initialized;

#else /* CONFIG_SMP */
diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
index 99ea5986038c..12501543c56d 100644
--- a/kernel/sched/topology.c
+++ b/kernel/sched/topology.c
@@ -497,7 +497,7 @@ void rq_attach_root(struct rq *rq, struct root_domain *rd)
old_rd = rq->rd;

if (cpumask_test_cpu(rq->cpu, old_rd->online))
- set_rq_offline(rq);
+ set_rq_offline(rq, RQ_ONOFF_TOPOLOGY);

cpumask_clear_cpu(rq->cpu, old_rd->span);

@@ -515,7 +515,7 @@ void rq_attach_root(struct rq *rq, struct root_domain *rd)

cpumask_set_cpu(rq->cpu, rd->span);
if (cpumask_test_cpu(rq->cpu, cpu_active_mask))
- set_rq_online(rq);
+ set_rq_online(rq, RQ_ONOFF_TOPOLOGY);

rq_unlock_irqrestore(rq, &rf);

--
2.44.0