[RESEND x3][PATCH v12 6/7] sched: Split out __schedule() deactivate task logic into a helper

From: John Stultz
Date: Wed Oct 09 2024 - 19:55:17 EST


As we're going to re-use the deactivation logic,
split it into a helper.

Cc: Joel Fernandes <joelaf@xxxxxxxxxx>
Cc: Qais Yousef <qyousef@xxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Juri Lelli <juri.lelli@xxxxxxxxxx>
Cc: Vincent Guittot <vincent.guittot@xxxxxxxxxx>
Cc: Dietmar Eggemann <dietmar.eggemann@xxxxxxx>
Cc: Valentin Schneider <vschneid@xxxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Ben Segall <bsegall@xxxxxxxxxx>
Cc: Zimuzo Ezeozue <zezeozue@xxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxx>
Cc: Will Deacon <will@xxxxxxxxxx>
Cc: Waiman Long <longman@xxxxxxxxxx>
Cc: Boqun Feng <boqun.feng@xxxxxxxxx>
Cc: "Paul E. McKenney" <paulmck@xxxxxxxxxx>
Cc: Metin Kaya <Metin.Kaya@xxxxxxx>
Cc: Xuewen Yan <xuewen.yan94@xxxxxxxxx>
Cc: K Prateek Nayak <kprateek.nayak@xxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Daniel Lezcano <daniel.lezcano@xxxxxxxxxx>
Cc: kernel-team@xxxxxxxxxxx
Tested-by: K Prateek Nayak <kprateek.nayak@xxxxxxx>
Tested-by: Metin Kaya <metin.kaya@xxxxxxx>
Reviewed-by: Metin Kaya <metin.kaya@xxxxxxx>
Reviewed-by: Qais Yousef <qyousef@xxxxxxxxxxx>
Signed-off-by: John Stultz <jstultz@xxxxxxxxxx>
---
v6:
* Define function as static to avoid "no previous prototype"
warnings as Reported-by: kernel test robot <lkp@xxxxxxxxx>
v7:
* Rename state task_state to be more clear, as suggested by
Metin Kaya
v11:
* Return early to simplify indentation, and drop unused bool
return (will be introduced later when its needed) as sugggested
by Qais.
---
kernel/sched/core.c | 65 +++++++++++++++++++++++++++------------------
1 file changed, 39 insertions(+), 26 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 615fc7a7b17c..7f949bb9e2a8 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -6483,6 +6483,44 @@ pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
#define SM_PREEMPT 1
#define SM_RTLOCK_WAIT 2

+/*
+ * Helper function for __schedule()
+ *
+ * If a task does not have signals pending, deactivate it
+ * Otherwise marks the task's __state as RUNNING
+ */
+static void try_to_deactivate_task(struct rq *rq, struct task_struct *p,
+ unsigned long task_state)
+{
+ int flags = DEQUEUE_NOCLOCK;
+
+ if (signal_pending_state(task_state, p)) {
+ WRITE_ONCE(p->__state, TASK_RUNNING);
+ return;
+ }
+
+ p->sched_contributes_to_load =
+ (task_state & TASK_UNINTERRUPTIBLE) &&
+ !(task_state & TASK_NOLOAD) &&
+ !(task_state & TASK_FROZEN);
+
+ if (unlikely(is_special_task_state(task_state)))
+ flags |= DEQUEUE_SPECIAL;
+
+ /*
+ * __schedule() ttwu()
+ * prev_state = prev->state; if (p->on_rq && ...)
+ * if (prev_state) goto out;
+ * p->on_rq = 0; smp_acquire__after_ctrl_dep();
+ * p->state = TASK_WAKING
+ *
+ * Where __schedule() and ttwu() have matching control dependencies.
+ *
+ * After this, schedule() must not care about p->state any more.
+ */
+ block_task(rq, p, flags);
+}
+
/*
* __schedule() is the main scheduler function.
*
@@ -6590,32 +6628,7 @@ static void __sched notrace __schedule(int sched_mode)
goto picked;
}
} else if (!preempt && prev_state) {
- if (signal_pending_state(prev_state, prev)) {
- WRITE_ONCE(prev->__state, TASK_RUNNING);
- } else {
- int flags = DEQUEUE_NOCLOCK;
-
- prev->sched_contributes_to_load =
- (prev_state & TASK_UNINTERRUPTIBLE) &&
- !(prev_state & TASK_NOLOAD) &&
- !(prev_state & TASK_FROZEN);
-
- if (unlikely(is_special_task_state(prev_state)))
- flags |= DEQUEUE_SPECIAL;
-
- /*
- * __schedule() ttwu()
- * prev_state = prev->state; if (p->on_rq && ...)
- * if (prev_state) goto out;
- * p->on_rq = 0; smp_acquire__after_ctrl_dep();
- * p->state = TASK_WAKING
- *
- * Where __schedule() and ttwu() have matching control dependencies.
- *
- * After this, schedule() must not care about p->state any more.
- */
- block_task(rq, prev, flags);
- }
+ try_to_deactivate_task(rq, prev, prev_state);
switch_count = &prev->nvcsw;
}

--
2.47.0.rc0.187.ge670bccf7e-goog