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Message-ID: <176060720216.709179.6681961039422919924.tip-bot2@tip-bot2>
Date: Thu, 16 Oct 2025 09:33:22 -0000
From: "tip-bot2 for Peter Zijlstra" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: "Peter Zijlstra (Intel)" <peterz@...radead.org>, Tejun Heo <tj@...nel.org>,
x86@...nel.org, linux-kernel@...r.kernel.org
Subject: [tip: sched/core] sched: Detect per-class runqueue changes
The following commit has been merged into the sched/core branch of tip:
Commit-ID: 1e900f415c6082cd4bcdae4c92515d21fb389473
Gitweb: https://git.kernel.org/tip/1e900f415c6082cd4bcdae4c92515d21fb389473
Author: Peter Zijlstra <peterz@...radead.org>
AuthorDate: Wed, 01 Oct 2025 15:50:15 +02:00
Committer: Peter Zijlstra <peterz@...radead.org>
CommitterDate: Thu, 16 Oct 2025 11:13:55 +02:00
sched: Detect per-class runqueue changes
Have enqueue/dequeue set a per-class bit in rq->queue_mask. This then
enables easy tracking of which runqueues are modified over a
lock-break.
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Acked-by: Tejun Heo <tj@...nel.org>
---
kernel/sched/core.c | 2 ++
kernel/sched/deadline.c | 2 ++
kernel/sched/ext.c | 2 ++
kernel/sched/fair.c | 7 +++++--
kernel/sched/idle.c | 2 ++
kernel/sched/rt.c | 2 ++
kernel/sched/sched.h | 25 +++++++++++++++++++++++++
kernel/sched/stop_task.c | 2 ++
8 files changed, 42 insertions(+), 2 deletions(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index e2199e4..9fc990f 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2089,6 +2089,7 @@ void enqueue_task(struct rq *rq, struct task_struct *p, int flags)
*/
uclamp_rq_inc(rq, p, flags);
+ rq->queue_mask |= p->sched_class->queue_mask;
p->sched_class->enqueue_task(rq, p, flags);
psi_enqueue(p, flags);
@@ -2121,6 +2122,7 @@ inline bool dequeue_task(struct rq *rq, struct task_struct *p, int flags)
* and mark the task ->sched_delayed.
*/
uclamp_rq_dec(rq, p);
+ rq->queue_mask |= p->sched_class->queue_mask;
return p->sched_class->dequeue_task(rq, p, flags);
}
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 1f94994..83e6175 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -3092,6 +3092,8 @@ static int task_is_throttled_dl(struct task_struct *p, int cpu)
DEFINE_SCHED_CLASS(dl) = {
+ .queue_mask = 8,
+
.enqueue_task = enqueue_task_dl,
.dequeue_task = dequeue_task_dl,
.yield_task = yield_task_dl,
diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
index 5717042..949c3a6 100644
--- a/kernel/sched/ext.c
+++ b/kernel/sched/ext.c
@@ -3234,6 +3234,8 @@ static void scx_cgroup_unlock(void) {}
* their current sched_class. Call them directly from sched core instead.
*/
DEFINE_SCHED_CLASS(ext) = {
+ .queue_mask = 1,
+
.enqueue_task = enqueue_task_scx,
.dequeue_task = dequeue_task_scx,
.yield_task = yield_task_scx,
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 77a713e..23ac05c 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -12841,6 +12841,7 @@ static int sched_balance_newidle(struct rq *this_rq, struct rq_flags *rf)
}
rcu_read_unlock();
+ rq_modified_clear(this_rq);
raw_spin_rq_unlock(this_rq);
t0 = sched_clock_cpu(this_cpu);
@@ -12898,8 +12899,8 @@ static int sched_balance_newidle(struct rq *this_rq, struct rq_flags *rf)
if (this_rq->cfs.h_nr_queued && !pulled_task)
pulled_task = 1;
- /* Is there a task of a high priority class? */
- if (this_rq->nr_running != this_rq->cfs.h_nr_queued)
+ /* If a higher prio class was modified, restart the pick */
+ if (rq_modified_above(this_rq, &fair_sched_class))
pulled_task = -1;
out:
@@ -13633,6 +13634,8 @@ static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task
*/
DEFINE_SCHED_CLASS(fair) = {
+ .queue_mask = 2,
+
.enqueue_task = enqueue_task_fair,
.dequeue_task = dequeue_task_fair,
.yield_task = yield_task_fair,
diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c
index dee6e01..055b0dd 100644
--- a/kernel/sched/idle.c
+++ b/kernel/sched/idle.c
@@ -521,6 +521,8 @@ static void update_curr_idle(struct rq *rq)
*/
DEFINE_SCHED_CLASS(idle) = {
+ .queue_mask = 0,
+
/* no enqueue/yield_task for idle tasks */
/* dequeue is not valid, we print a debug message there: */
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index c2347e4..9bc828d 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -2569,6 +2569,8 @@ static int task_is_throttled_rt(struct task_struct *p, int cpu)
DEFINE_SCHED_CLASS(rt) = {
+ .queue_mask = 4,
+
.enqueue_task = enqueue_task_rt,
.dequeue_task = dequeue_task_rt,
.yield_task = yield_task_rt,
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index e3d2710..f4a3230 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1118,6 +1118,8 @@ struct rq {
/* runqueue lock: */
raw_spinlock_t __lock;
+ /* Per class runqueue modification mask; bits in class order. */
+ unsigned int queue_mask;
unsigned int nr_running;
#ifdef CONFIG_NUMA_BALANCING
unsigned int nr_numa_running;
@@ -2414,6 +2416,15 @@ struct sched_class {
#ifdef CONFIG_UCLAMP_TASK
int uclamp_enabled;
#endif
+ /*
+ * idle: 0
+ * ext: 1
+ * fair: 2
+ * rt: 4
+ * dl: 8
+ * stop: 16
+ */
+ unsigned int queue_mask;
/*
* move_queued_task/activate_task/enqueue_task: rq->lock
@@ -2571,6 +2582,20 @@ struct sched_class {
#endif
};
+/*
+ * Does not nest; only used around sched_class::pick_task() rq-lock-breaks.
+ */
+static inline void rq_modified_clear(struct rq *rq)
+{
+ rq->queue_mask = 0;
+}
+
+static inline bool rq_modified_above(struct rq *rq, const struct sched_class * class)
+{
+ unsigned int mask = class->queue_mask;
+ return rq->queue_mask & ~((mask << 1) - 1);
+}
+
static inline void put_prev_task(struct rq *rq, struct task_struct *prev)
{
WARN_ON_ONCE(rq->donor != prev);
diff --git a/kernel/sched/stop_task.c b/kernel/sched/stop_task.c
index 73aa8de..d98c453 100644
--- a/kernel/sched/stop_task.c
+++ b/kernel/sched/stop_task.c
@@ -98,6 +98,8 @@ static void update_curr_stop(struct rq *rq)
*/
DEFINE_SCHED_CLASS(stop) = {
+ .queue_mask = 16,
+
.enqueue_task = enqueue_task_stop,
.dequeue_task = dequeue_task_stop,
.yield_task = yield_task_stop,
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