Adding upstream version 6.9.7.upstream/6.9.7

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 57 insertions, 85 deletions

diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index 6d6e540bac..73ef0dabc3 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -202,6 +202,14 @@ struct cpuset {
 };
 
 /*
+ * Legacy hierarchy call to cgroup_transfer_tasks() is handled asynchrously
+ */
+struct cpuset_remove_tasks_struct {
+	struct work_struct work;
+	struct cpuset *cs;
+};
+
+/*
  * Exclusive CPUs distributed out to sub-partitions of top_cpuset
  */
 static cpumask_var_t	subpartitions_cpus;
@@ -449,12 +457,6 @@ static DEFINE_SPINLOCK(callback_lock);
 
 static struct workqueue_struct *cpuset_migrate_mm_wq;
 
-/*
- * CPU / memory hotplug is handled asynchronously.
- */
-static void cpuset_hotplug_workfn(struct work_struct *work);
-static DECLARE_WORK(cpuset_hotplug_work, cpuset_hotplug_workfn);
-
 static DECLARE_WAIT_QUEUE_HEAD(cpuset_attach_wq);
 
 static inline void check_insane_mems_config(nodemask_t *nodes)
@@ -540,22 +542,10 @@ static void guarantee_online_cpus(struct task_struct *tsk,
 	rcu_read_lock();
 	cs = task_cs(tsk);
 
-	while (!cpumask_intersects(cs->effective_cpus, pmask)) {
+	while (!cpumask_intersects(cs->effective_cpus, pmask))
 		cs = parent_cs(cs);
-		if (unlikely(!cs)) {
-			/*
-			 * The top cpuset doesn't have any online cpu as a
-			 * consequence of a race between cpuset_hotplug_work
-			 * and cpu hotplug notifier.  But we know the top
-			 * cpuset's effective_cpus is on its way to be
-			 * identical to cpu_online_mask.
-			 */
-			goto out_unlock;
-		}
-	}
-	cpumask_and(pmask, pmask, cs->effective_cpus);
 
-out_unlock:
+	cpumask_and(pmask, pmask, cs->effective_cpus);
 	rcu_read_unlock();
 }
 
@@ -1217,7 +1207,7 @@ static void rebuild_sched_domains_locked(void)
 	/*
 	 * If we have raced with CPU hotplug, return early to avoid
 	 * passing doms with offlined cpu to partition_sched_domains().
-	 * Anyways, cpuset_hotplug_workfn() will rebuild sched domains.
+	 * Anyways, cpuset_handle_hotplug() will rebuild sched domains.
 	 *
 	 * With no CPUs in any subpartitions, top_cpuset's effective CPUs
 	 * should be the same as the active CPUs, so checking only top_cpuset
@@ -1260,12 +1250,17 @@ static void rebuild_sched_domains_locked(void)
 }
 #endif /* CONFIG_SMP */
 
-void rebuild_sched_domains(void)
+static void rebuild_sched_domains_cpuslocked(void)
 {
-	cpus_read_lock();
 	mutex_lock(&cpuset_mutex);
 	rebuild_sched_domains_locked();
 	mutex_unlock(&cpuset_mutex);
+}
+
+void rebuild_sched_domains(void)
+{
+	cpus_read_lock();
+	rebuild_sched_domains_cpuslocked();
 	cpus_read_unlock();
 }
 
@@ -2079,14 +2074,11 @@ write_error:
 
 	/*
 	 * For partcmd_update without newmask, it is being called from
-	 * cpuset_hotplug_workfn() where cpus_read_lock() wasn't taken.
-	 * Update the load balance flag and scheduling domain if
-	 * cpus_read_trylock() is successful.
+	 * cpuset_handle_hotplug(). Update the load balance flag and
+	 * scheduling domain accordingly.
 	 */
-	if ((cmd == partcmd_update) && !newmask && cpus_read_trylock()) {
+	if ((cmd == partcmd_update) && !newmask)
 		update_partition_sd_lb(cs, old_prs);
-		cpus_read_unlock();
-	}
 
 	notify_partition_change(cs, old_prs);
 	return 0;
@@ -3599,8 +3591,8 @@ static ssize_t cpuset_write_resmask(struct kernfs_open_file *of,
 	 * proceeding, so that we don't end up keep removing tasks added
 	 * after execution capability is restored.
 	 *
-	 * cpuset_hotplug_work calls back into cgroup core via
-	 * cgroup_transfer_tasks() and waiting for it from a cgroupfs
+	 * cpuset_handle_hotplug may call back into cgroup core asynchronously
+	 * via cgroup_transfer_tasks() and waiting for it from a cgroupfs
 	 * operation like this one can lead to a deadlock through kernfs
 	 * active_ref protection.  Let's break the protection.  Losing the
 	 * protection is okay as we check whether @cs is online after
@@ -3609,7 +3601,6 @@ static ssize_t cpuset_write_resmask(struct kernfs_open_file *of,
 	 */
 	css_get(&cs->css);
 	kernfs_break_active_protection(of->kn);
-	flush_work(&cpuset_hotplug_work);
 
 	cpus_read_lock();
 	mutex_lock(&cpuset_mutex);
@@ -3897,6 +3888,7 @@ static struct cftype legacy_files[] = {
 	},
 
 	{
+		/* obsolete, may be removed in the future */
 		.name = "memory_spread_slab",
 		.read_u64 = cpuset_read_u64,
 		.write_u64 = cpuset_write_u64,
@@ -4353,6 +4345,16 @@ static void remove_tasks_in_empty_cpuset(struct cpuset *cs)
 	}
 }
 
+static void cpuset_migrate_tasks_workfn(struct work_struct *work)
+{
+	struct cpuset_remove_tasks_struct *s;
+
+	s = container_of(work, struct cpuset_remove_tasks_struct, work);
+	remove_tasks_in_empty_cpuset(s->cs);
+	css_put(&s->cs->css);
+	kfree(s);
+}
+
 static void
 hotplug_update_tasks_legacy(struct cpuset *cs,
 			    struct cpumask *new_cpus, nodemask_t *new_mems,
@@ -4382,12 +4384,21 @@ hotplug_update_tasks_legacy(struct cpuset *cs,
 	/*
 	 * Move tasks to the nearest ancestor with execution resources,
 	 * This is full cgroup operation which will also call back into
-	 * cpuset. Should be done outside any lock.
+	 * cpuset. Execute it asynchronously using workqueue.
 	 */
-	if (is_empty) {
-		mutex_unlock(&cpuset_mutex);
-		remove_tasks_in_empty_cpuset(cs);
-		mutex_lock(&cpuset_mutex);
+	if (is_empty && cs->css.cgroup->nr_populated_csets &&
+	    css_tryget_online(&cs->css)) {
+		struct cpuset_remove_tasks_struct *s;
+
+		s = kzalloc(sizeof(*s), GFP_KERNEL);
+		if (WARN_ON_ONCE(!s)) {
+			css_put(&cs->css);
+			return;
+		}
+
+		s->cs = cs;
+		INIT_WORK(&s->work, cpuset_migrate_tasks_workfn);
+		schedule_work(&s->work);
 	}
 }
 
@@ -4420,30 +4431,6 @@ void cpuset_force_rebuild(void)
 	force_rebuild = true;
 }
 
-/*
- * Attempt to acquire a cpus_read_lock while a hotplug operation may be in
- * progress.
- * Return: true if successful, false otherwise
- *
- * To avoid circular lock dependency between cpuset_mutex and cpus_read_lock,
- * cpus_read_trylock() is used here to acquire the lock.
- */
-static bool cpuset_hotplug_cpus_read_trylock(void)
-{
-	int retries = 0;
-
-	while (!cpus_read_trylock()) {
-		/*
-		 * CPU hotplug still in progress. Retry 5 times
-		 * with a 10ms wait before bailing out.
-		 */
-		if (++retries > 5)
-			return false;
-		msleep(10);
-	}
-	return true;
-}
-
 /**
  * cpuset_hotplug_update_tasks - update tasks in a cpuset for hotunplug
  * @cs: cpuset in interest
@@ -4492,13 +4479,11 @@ retry:
 		compute_partition_effective_cpumask(cs, &new_cpus);
 
 	if (remote && cpumask_empty(&new_cpus) &&
-	    partition_is_populated(cs, NULL) &&
-	    cpuset_hotplug_cpus_read_trylock()) {
+	    partition_is_populated(cs, NULL)) {
 		remote_partition_disable(cs, tmp);
 		compute_effective_cpumask(&new_cpus, cs, parent);
 		remote = false;
 		cpuset_force_rebuild();
-		cpus_read_unlock();
 	}
 
 	/*
@@ -4518,18 +4503,8 @@ retry:
 	else if (is_partition_valid(parent) && is_partition_invalid(cs))
 		partcmd = partcmd_update;
 
-	/*
-	 * cpus_read_lock needs to be held before calling
-	 * update_parent_effective_cpumask(). To avoid circular lock
-	 * dependency between cpuset_mutex and cpus_read_lock,
-	 * cpus_read_trylock() is used here to acquire the lock.
-	 */
 	if (partcmd >= 0) {
-		if (!cpuset_hotplug_cpus_read_trylock())
-			goto update_tasks;
-
 		update_parent_effective_cpumask(cs, partcmd, NULL, tmp);
-		cpus_read_unlock();
 		if ((partcmd == partcmd_invalidate) || is_partition_valid(cs)) {
 			compute_partition_effective_cpumask(cs, &new_cpus);
 			cpuset_force_rebuild();
@@ -4557,8 +4532,7 @@ unlock:
 }
 
 /**
- * cpuset_hotplug_workfn - handle CPU/memory hotunplug for a cpuset
- * @work: unused
+ * cpuset_handle_hotplug - handle CPU/memory hot{,un}plug for a cpuset
  *
  * This function is called after either CPU or memory configuration has
  * changed and updates cpuset accordingly.  The top_cpuset is always
@@ -4572,8 +4546,10 @@ unlock:
  *
  * Note that CPU offlining during suspend is ignored.  We don't modify
  * cpusets across suspend/resume cycles at all.
+ *
+ * CPU / memory hotplug is handled synchronously.
  */
-static void cpuset_hotplug_workfn(struct work_struct *work)
+static void cpuset_handle_hotplug(void)
 {
 	static cpumask_t new_cpus;
 	static nodemask_t new_mems;
@@ -4584,6 +4560,7 @@ static void cpuset_hotplug_workfn(struct work_struct *work)
 	if (on_dfl && !alloc_cpumasks(NULL, &tmp))
 		ptmp = &tmp;
 
+	lockdep_assert_cpus_held();
 	mutex_lock(&cpuset_mutex);
 
 	/* fetch the available cpus/mems and find out which changed how */
@@ -4665,7 +4642,7 @@ static void cpuset_hotplug_workfn(struct work_struct *work)
 	/* rebuild sched domains if cpus_allowed has changed */
 	if (cpus_updated || force_rebuild) {
 		force_rebuild = false;
-		rebuild_sched_domains();
+		rebuild_sched_domains_cpuslocked();
 	}
 
 	free_cpumasks(NULL, ptmp);
@@ -4678,12 +4655,7 @@ void cpuset_update_active_cpus(void)
 	 * inside cgroup synchronization.  Bounce actual hotplug processing
 	 * to a work item to avoid reverse locking order.
 	 */
-	schedule_work(&cpuset_hotplug_work);
-}
-
-void cpuset_wait_for_hotplug(void)
-{
-	flush_work(&cpuset_hotplug_work);
+	cpuset_handle_hotplug();
 }
 
 /*
@@ -4694,7 +4666,7 @@ void cpuset_wait_for_hotplug(void)
 static int cpuset_track_online_nodes(struct notifier_block *self,
 				unsigned long action, void *arg)
 {
-	schedule_work(&cpuset_hotplug_work);
+	cpuset_handle_hotplug();
 	return NOTIFY_OK;
 }