linux-kernel - [PATCH 1/3] sched/core: Make select_task_rq() take the pointer to wake

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Message-ID: <20240927234838.152112-2-tj@kernel.org>
Date: Fri, 27 Sep 2024 13:46:11 -1000
From: Tejun Heo <tj@...nel.org>
To: void@...ifault.com,
	peterz@...radead.org,
	mingo@...hat.com
Cc: kernel-team@...a.com,
	linux-kernel@...r.kernel.org,
	sched-ext@...a.com,
	Tejun Heo <tj@...nel.org>
Subject: [PATCH 1/3] sched/core: Make select_task_rq() take the pointer to wake_flags instead of value

This will be used to allow select_task_rq() to indicate whether
->select_task_rq() was called by modifying *wake_flags.

This makes try_to_wake_up() call all functions that take wake_flags with
WF_TTWU set. Previously, only select_task_rq() was. Using the same flags is
more consistent, and, as the flag is only tested by ->select_task_rq()
implementations, it doesn't cause any behavior differences.

Signed-off-by: Tejun Heo <tj@...nel.org>
---
 kernel/sched/core.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 43e453ab7e20..e70b57a5693e 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -3518,12 +3518,12 @@ static int select_fallback_rq(int cpu, struct task_struct *p)
  * The caller (fork, wakeup) owns p->pi_lock, ->cpus_ptr is stable.
  */
 static inline
-int select_task_rq(struct task_struct *p, int cpu, int wake_flags)
+int select_task_rq(struct task_struct *p, int cpu, int *wake_flags)
 {
 	lockdep_assert_held(&p->pi_lock);
 
 	if (p->nr_cpus_allowed > 1 && !is_migration_disabled(p))
-		cpu = p->sched_class->select_task_rq(p, cpu, wake_flags);
+		cpu = p->sched_class->select_task_rq(p, cpu, *wake_flags);
 	else
 		cpu = cpumask_any(p->cpus_ptr);
 
@@ -4120,6 +4120,8 @@ int try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)
 	guard(preempt)();
 	int cpu, success = 0;
 
+	wake_flags |= WF_TTWU;
+
 	if (p == current) {
 		/*
 		 * We're waking current, this means 'p->on_rq' and 'task_cpu(p)
@@ -4252,7 +4254,7 @@ int try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)
 		 */
 		smp_cond_load_acquire(&p->on_cpu, !VAL);
 
-		cpu = select_task_rq(p, p->wake_cpu, wake_flags | WF_TTWU);
+		cpu = select_task_rq(p, p->wake_cpu, &wake_flags);
 		if (task_cpu(p) != cpu) {
 			if (p->in_iowait) {
 				delayacct_blkio_end(p);
@@ -4793,6 +4795,7 @@ void wake_up_new_task(struct task_struct *p)
 {
 	struct rq_flags rf;
 	struct rq *rq;
+	int wake_flags = WF_FORK;
 
 	raw_spin_lock_irqsave(&p->pi_lock, rf.flags);
 	WRITE_ONCE(p->__state, TASK_RUNNING);
@@ -4807,7 +4810,7 @@ void wake_up_new_task(struct task_struct *p)
 	 */
 	p->recent_used_cpu = task_cpu(p);
 	rseq_migrate(p);
-	__set_task_cpu(p, select_task_rq(p, task_cpu(p), WF_FORK));
+	__set_task_cpu(p, select_task_rq(p, task_cpu(p), &wake_flags));
 #endif
 	rq = __task_rq_lock(p, &rf);
 	update_rq_clock(rq);
@@ -4815,7 +4818,7 @@ void wake_up_new_task(struct task_struct *p)
 
 	activate_task(rq, p, ENQUEUE_NOCLOCK | ENQUEUE_INITIAL);
 	trace_sched_wakeup_new(p);
-	wakeup_preempt(rq, p, WF_FORK);
+	wakeup_preempt(rq, p, wake_flags);
 #ifdef CONFIG_SMP
 	if (p->sched_class->task_woken) {
 		/*
-- 
2.46.2