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From:   Domenico Cerasuolo <cerasuolodomenico@gmail.com>
To:     linux-kernel@vger.kernel.org
Cc:     peterz@infradead.org, surenb@google.com, brauner@kernel.org,
        chris@chrisdown.name, hannes@cmpxchg.org,
        Domenico Cerasuolo <cerasuolodomenico@gmail.com>
Subject: [PATCH v6 2/4] sched/psi: rename existing poll members in preparation
Date:   Thu, 30 Mar 2023 12:54:16 +0200
Message-Id: <20230330105418.77061-3-cerasuolodomenico@gmail.com>
In-Reply-To: <20230330105418.77061-1-cerasuolodomenico@gmail.com>
References: <20230330105418.77061-1-cerasuolodomenico@gmail.com>
MIME-Version: 1.0
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Renaming in PSI implementation to make a clear distinction between
privileged and unprivileged triggers code to be implemented in the
next patch.

Suggested-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Domenico Cerasuolo <cerasuolodomenico@gmail.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
---
 include/linux/psi_types.h |  36 ++++-----
 kernel/sched/psi.c        | 163 +++++++++++++++++++-------------------
 2 files changed, 100 insertions(+), 99 deletions(-)

diff --git a/include/linux/psi_types.h b/include/linux/psi_types.h
index 1e0a0d7ace3a..1819afa8b198 100644
--- a/include/linux/psi_types.h
+++ b/include/linux/psi_types.h
@@ -175,26 +175,26 @@ struct psi_group {
 	u64 total[NR_PSI_AGGREGATORS][NR_PSI_STATES - 1];
 	unsigned long avg[NR_PSI_STATES - 1][3];
 
-	/* Monitor work control */
-	struct task_struct __rcu *poll_task;
-	struct timer_list poll_timer;
-	wait_queue_head_t poll_wait;
-	atomic_t poll_wakeup;
-	atomic_t poll_scheduled;
+	/* Monitor RT polling work control */
+	struct task_struct __rcu *rtpoll_task;
+	struct timer_list rtpoll_timer;
+	wait_queue_head_t rtpoll_wait;
+	atomic_t rtpoll_wakeup;
+	atomic_t rtpoll_scheduled;
 
 	/* Protects data used by the monitor */
-	struct mutex trigger_lock;
-
-	/* Configured polling triggers */
-	struct list_head triggers;
-	u32 nr_triggers[NR_PSI_STATES - 1];
-	u32 poll_states;
-	u64 poll_min_period;
-
-	/* Total stall times at the start of monitor activation */
-	u64 polling_total[NR_PSI_STATES - 1];
-	u64 polling_next_update;
-	u64 polling_until;
+	struct mutex rtpoll_trigger_lock;
+
+	/* Configured RT polling triggers */
+	struct list_head rtpoll_triggers;
+	u32 rtpoll_nr_triggers[NR_PSI_STATES - 1];
+	u32 rtpoll_states;
+	u64 rtpoll_min_period;
+
+	/* Total stall times at the start of RT polling monitor activation */
+	u64 rtpoll_total[NR_PSI_STATES - 1];
+	u64 rtpoll_next_update;
+	u64 rtpoll_until;
 };
 
 #else /* CONFIG_PSI */
diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c
index fe9269f1d2a4..a3d0b5cf797a 100644
--- a/kernel/sched/psi.c
+++ b/kernel/sched/psi.c
@@ -189,14 +189,14 @@ static void group_init(struct psi_group *group)
 	INIT_DELAYED_WORK(&group->avgs_work, psi_avgs_work);
 	mutex_init(&group->avgs_lock);
 	/* Init trigger-related members */
-	atomic_set(&group->poll_scheduled, 0);
-	mutex_init(&group->trigger_lock);
-	INIT_LIST_HEAD(&group->triggers);
-	group->poll_min_period = U32_MAX;
-	group->polling_next_update = ULLONG_MAX;
-	init_waitqueue_head(&group->poll_wait);
-	timer_setup(&group->poll_timer, poll_timer_fn, 0);
-	rcu_assign_pointer(group->poll_task, NULL);
+	atomic_set(&group->rtpoll_scheduled, 0);
+	mutex_init(&group->rtpoll_trigger_lock);
+	INIT_LIST_HEAD(&group->rtpoll_triggers);
+	group->rtpoll_min_period = U32_MAX;
+	group->rtpoll_next_update = ULLONG_MAX;
+	init_waitqueue_head(&group->rtpoll_wait);
+	timer_setup(&group->rtpoll_timer, poll_timer_fn, 0);
+	rcu_assign_pointer(group->rtpoll_task, NULL);
 }
 
 void __init psi_init(void)
@@ -440,11 +440,11 @@ static u64 update_triggers(struct psi_group *group, u64 now)
 	 * On subsequent updates, calculate growth deltas and let
 	 * watchers know when their specified thresholds are exceeded.
 	 */
-	list_for_each_entry(t, &group->triggers, node) {
+	list_for_each_entry(t, &group->rtpoll_triggers, node) {
 		u64 growth;
 		bool new_stall;
 
-		new_stall = group->polling_total[t->state] != total[t->state];
+		new_stall = group->rtpoll_total[t->state] != total[t->state];
 
 		/* Check for stall activity or a previous threshold breach */
 		if (!new_stall && !t->pending_event)
@@ -486,10 +486,10 @@ static u64 update_triggers(struct psi_group *group, u64 now)
 	}
 
 	if (update_total)
-		memcpy(group->polling_total, total,
-				sizeof(group->polling_total));
+		memcpy(group->rtpoll_total, total,
+				sizeof(group->rtpoll_total));
 
-	return now + group->poll_min_period;
+	return now + group->rtpoll_min_period;
 }
 
 static u64 update_averages(struct psi_group *group, u64 now)
@@ -582,53 +582,53 @@ static void init_triggers(struct psi_group *group, u64 now)
 {
 	struct psi_trigger *t;
 
-	list_for_each_entry(t, &group->triggers, node)
+	list_for_each_entry(t, &group->rtpoll_triggers, node)
 		window_reset(&t->win, now,
 				group->total[PSI_POLL][t->state], 0);
-	memcpy(group->polling_total, group->total[PSI_POLL],
-		   sizeof(group->polling_total));
-	group->polling_next_update = now + group->poll_min_period;
+	memcpy(group->rtpoll_total, group->total[PSI_POLL],
+		   sizeof(group->rtpoll_total));
+	group->rtpoll_next_update = now + group->rtpoll_min_period;
 }
 
 /* Schedule polling if it's not already scheduled or forced. */
-static void psi_schedule_poll_work(struct psi_group *group, unsigned long delay,
+static void psi_schedule_rtpoll_work(struct psi_group *group, unsigned long delay,
 				   bool force)
 {
 	struct task_struct *task;
 
 	/*
 	 * atomic_xchg should be called even when !force to provide a
-	 * full memory barrier (see the comment inside psi_poll_work).
+	 * full memory barrier (see the comment inside psi_rtpoll_work).
 	 */
-	if (atomic_xchg(&group->poll_scheduled, 1) && !force)
+	if (atomic_xchg(&group->rtpoll_scheduled, 1) && !force)
 		return;
 
 	rcu_read_lock();
 
-	task = rcu_dereference(group->poll_task);
+	task = rcu_dereference(group->rtpoll_task);
 	/*
 	 * kworker might be NULL in case psi_trigger_destroy races with
 	 * psi_task_change (hotpath) which can't use locks
 	 */
 	if (likely(task))
-		mod_timer(&group->poll_timer, jiffies + delay);
+		mod_timer(&group->rtpoll_timer, jiffies + delay);
 	else
-		atomic_set(&group->poll_scheduled, 0);
+		atomic_set(&group->rtpoll_scheduled, 0);
 
 	rcu_read_unlock();
 }
 
-static void psi_poll_work(struct psi_group *group)
+static void psi_rtpoll_work(struct psi_group *group)
 {
 	bool force_reschedule = false;
 	u32 changed_states;
 	u64 now;
 
-	mutex_lock(&group->trigger_lock);
+	mutex_lock(&group->rtpoll_trigger_lock);
 
 	now = sched_clock();
 
-	if (now > group->polling_until) {
+	if (now > group->rtpoll_until) {
 		/*
 		 * We are either about to start or might stop polling if no
 		 * state change was recorded. Resetting poll_scheduled leaves
@@ -638,7 +638,7 @@ static void psi_poll_work(struct psi_group *group)
 		 * should be negligible and polling_next_update still keeps
 		 * updates correctly on schedule.
 		 */
-		atomic_set(&group->poll_scheduled, 0);
+		atomic_set(&group->rtpoll_scheduled, 0);
 		/*
 		 * A task change can race with the poll worker that is supposed to
 		 * report on it. To avoid missing events, ensure ordering between
@@ -667,9 +667,9 @@ static void psi_poll_work(struct psi_group *group)
 
 	collect_percpu_times(group, PSI_POLL, &changed_states);
 
-	if (changed_states & group->poll_states) {
+	if (changed_states & group->rtpoll_states) {
 		/* Initialize trigger windows when entering polling mode */
-		if (now > group->polling_until)
+		if (now > group->rtpoll_until)
 			init_triggers(group, now);
 
 		/*
@@ -677,50 +677,50 @@ static void psi_poll_work(struct psi_group *group)
 		 * minimum tracking window as long as monitor states are
 		 * changing.
 		 */
-		group->polling_until = now +
-			group->poll_min_period * UPDATES_PER_WINDOW;
+		group->rtpoll_until = now +
+			group->rtpoll_min_period * UPDATES_PER_WINDOW;
 	}
 
-	if (now > group->polling_until) {
-		group->polling_next_update = ULLONG_MAX;
+	if (now > group->rtpoll_until) {
+		group->rtpoll_next_update = ULLONG_MAX;
 		goto out;
 	}
 
-	if (now >= group->polling_next_update)
-		group->polling_next_update = update_triggers(group, now);
+	if (now >= group->rtpoll_next_update)
+		group->rtpoll_next_update = update_triggers(group, now);
 
-	psi_schedule_poll_work(group,
-		nsecs_to_jiffies(group->polling_next_update - now) + 1,
+	psi_schedule_rtpoll_work(group,
+		nsecs_to_jiffies(group->rtpoll_next_update - now) + 1,
 		force_reschedule);
 
 out:
-	mutex_unlock(&group->trigger_lock);
+	mutex_unlock(&group->rtpoll_trigger_lock);
 }
 
-static int psi_poll_worker(void *data)
+static int psi_rtpoll_worker(void *data)
 {
 	struct psi_group *group = (struct psi_group *)data;
 
 	sched_set_fifo_low(current);
 
 	while (true) {
-		wait_event_interruptible(group->poll_wait,
-				atomic_cmpxchg(&group->poll_wakeup, 1, 0) ||
+		wait_event_interruptible(group->rtpoll_wait,
+				atomic_cmpxchg(&group->rtpoll_wakeup, 1, 0) ||
 				kthread_should_stop());
 		if (kthread_should_stop())
 			break;
 
-		psi_poll_work(group);
+		psi_rtpoll_work(group);
 	}
 	return 0;
 }
 
 static void poll_timer_fn(struct timer_list *t)
 {
-	struct psi_group *group = from_timer(group, t, poll_timer);
+	struct psi_group *group = from_timer(group, t, rtpoll_timer);
 
-	atomic_set(&group->poll_wakeup, 1);
-	wake_up_interruptible(&group->poll_wait);
+	atomic_set(&group->rtpoll_wakeup, 1);
+	wake_up_interruptible(&group->rtpoll_wait);
 }
 
 static void record_times(struct psi_group_cpu *groupc, u64 now)
@@ -851,8 +851,8 @@ static void psi_group_change(struct psi_group *group, int cpu,
 
 	write_seqcount_end(&groupc->seq);
 
-	if (state_mask & group->poll_states)
-		psi_schedule_poll_work(group, 1, false);
+	if (state_mask & group->rtpoll_states)
+		psi_schedule_rtpoll_work(group, 1, false);
 
 	if (wake_clock && !delayed_work_pending(&group->avgs_work))
 		schedule_delayed_work(&group->avgs_work, PSI_FREQ);
@@ -1005,8 +1005,8 @@ void psi_account_irqtime(struct task_struct *task, u32 delta)
 
 		write_seqcount_end(&groupc->seq);
 
-		if (group->poll_states & (1 << PSI_IRQ_FULL))
-			psi_schedule_poll_work(group, 1, false);
+		if (group->rtpoll_states & (1 << PSI_IRQ_FULL))
+			psi_schedule_rtpoll_work(group, 1, false);
 	} while ((group = group->parent));
 }
 #endif
@@ -1101,7 +1101,7 @@ void psi_cgroup_free(struct cgroup *cgroup)
 	cancel_delayed_work_sync(&cgroup->psi->avgs_work);
 	free_percpu(cgroup->psi->pcpu);
 	/* All triggers must be removed by now */
-	WARN_ONCE(cgroup->psi->poll_states, "psi: trigger leak\n");
+	WARN_ONCE(cgroup->psi->rtpoll_states, "psi: trigger leak\n");
 	kfree(cgroup->psi);
 }
 
@@ -1302,29 +1302,29 @@ struct psi_trigger *psi_trigger_create(struct psi_group *group,
 	init_waitqueue_head(&t->event_wait);
 	t->pending_event = false;
 
-	mutex_lock(&group->trigger_lock);
+	mutex_lock(&group->rtpoll_trigger_lock);
 
-	if (!rcu_access_pointer(group->poll_task)) {
+	if (!rcu_access_pointer(group->rtpoll_task)) {
 		struct task_struct *task;
 
-		task = kthread_create(psi_poll_worker, group, "psimon");
+		task = kthread_create(psi_rtpoll_worker, group, "psimon");
 		if (IS_ERR(task)) {
 			kfree(t);
-			mutex_unlock(&group->trigger_lock);
+			mutex_unlock(&group->rtpoll_trigger_lock);
 			return ERR_CAST(task);
 		}
-		atomic_set(&group->poll_wakeup, 0);
+		atomic_set(&group->rtpoll_wakeup, 0);
 		wake_up_process(task);
-		rcu_assign_pointer(group->poll_task, task);
+		rcu_assign_pointer(group->rtpoll_task, task);
 	}
 
-	list_add(&t->node, &group->triggers);
-	group->poll_min_period = min(group->poll_min_period,
+	list_add(&t->node, &group->rtpoll_triggers);
+	group->rtpoll_min_period = min(group->rtpoll_min_period,
 		div_u64(t->win.size, UPDATES_PER_WINDOW));
-	group->nr_triggers[t->state]++;
-	group->poll_states |= (1 << t->state);
+	group->rtpoll_nr_triggers[t->state]++;
+	group->rtpoll_states |= (1 << t->state);
 
-	mutex_unlock(&group->trigger_lock);
+	mutex_unlock(&group->rtpoll_trigger_lock);
 
 	return t;
 }
@@ -1349,51 +1349,52 @@ void psi_trigger_destroy(struct psi_trigger *t)
 	 */
 	wake_up_pollfree(&t->event_wait);
 
-	mutex_lock(&group->trigger_lock);
+	mutex_lock(&group->rtpoll_trigger_lock);
 
 	if (!list_empty(&t->node)) {
 		struct psi_trigger *tmp;
 		u64 period = ULLONG_MAX;
 
 		list_del(&t->node);
-		group->nr_triggers[t->state]--;
-		if (!group->nr_triggers[t->state])
-			group->poll_states &= ~(1 << t->state);
+		group->rtpoll_nr_triggers[t->state]--;
+		if (!group->rtpoll_nr_triggers[t->state])
+			group->rtpoll_states &= ~(1 << t->state);
 		/* reset min update period for the remaining triggers */
-		list_for_each_entry(tmp, &group->triggers, node)
+		list_for_each_entry(tmp, &group->rtpoll_triggers, node)
 			period = min(period, div_u64(tmp->win.size,
 					UPDATES_PER_WINDOW));
-		group->poll_min_period = period;
-		/* Destroy poll_task when the last trigger is destroyed */
-		if (group->poll_states == 0) {
-			group->polling_until = 0;
+		group->rtpoll_min_period = period;
+		/* Destroy rtpoll_task when the last trigger is destroyed */
+		if (group->rtpoll_states == 0) {
+			group->rtpoll_until = 0;
 			task_to_destroy = rcu_dereference_protected(
-					group->poll_task,
-					lockdep_is_held(&group->trigger_lock));
-			rcu_assign_pointer(group->poll_task, NULL);
-			del_timer(&group->poll_timer);
+					group->rtpoll_task,
+					lockdep_is_held(&group->rtpoll_trigger_lock));
+			rcu_assign_pointer(group->rtpoll_task, NULL);
+			del_timer(&group->rtpoll_timer);
 		}
 	}
 
-	mutex_unlock(&group->trigger_lock);
+	mutex_unlock(&group->rtpoll_trigger_lock);
 
 	/*
-	 * Wait for psi_schedule_poll_work RCU to complete its read-side
+	 * Wait for psi_schedule_rtpoll_work RCU to complete its read-side
 	 * critical section before destroying the trigger and optionally the
-	 * poll_task.
+	 * rtpoll_task.
 	 */
 	synchronize_rcu();
 	/*
-	 * Stop kthread 'psimon' after releasing trigger_lock to prevent a
-	 * deadlock while waiting for psi_poll_work to acquire trigger_lock
+	 * Stop kthread 'psimon' after releasing rtpoll_trigger_lock to prevent
+	 * a deadlock while waiting for psi_rtpoll_work to acquire
+	 * rtpoll_trigger_lock
 	 */
 	if (task_to_destroy) {
 		/*
 		 * After the RCU grace period has expired, the worker
-		 * can no longer be found through group->poll_task.
+		 * can no longer be found through group->rtpoll_task.
 		 */
 		kthread_stop(task_to_destroy);
-		atomic_set(&group->poll_scheduled, 0);
+		atomic_set(&group->rtpoll_scheduled, 0);
 	}
 	kfree(t);
 }
-- 
2.34.1