[PATCH 29/32] x86/intel_rdt_rdtgroup.c: Tasks iterator and write

[Fenghua Yu]

From: Fenghua Yu <fenghua.yu@xxxxxxxxx>

"tasks" file in rdtgroup contains task pids. User can move a task pid
to one directory. A task can only stay in one directory at the same
time.

Each rdtgroup contains a rg_list. When a pid is written to this
rdtgroup's tasks, the task's rg_list is added in the rdtgroup's
linked list and deleted from its previous rdtgroup's linked list.

When user reads the "tasks" file, all pids are shown in the order
from small to large.

Signed-off-by: Fenghua Yu <fenghua.yu@xxxxxxxxx>
Reviewed-by: Tony Luck <tony.luck@xxxxxxxxx>
---
 arch/x86/kernel/cpu/intel_rdt_rdtgroup.c | 138 +++++++++++++++++++++++++++++--
 1 file changed, 132 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c b/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c
index b5f42f5..e6e8757 100644
--- a/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c
+++ b/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c
@@ -76,8 +76,6 @@ static DEFINE_SPINLOCK(rdtgroup_idr_lock);
 
 struct percpu_rw_semaphore rdtgroup_threadgroup_rwsem;
 
-#define MAX_CPUMASK_CHAR_IN_HEX	(NR_CPUS/4)
-
 static struct rftype rdtgroup_root_base_files[];
 
 #define RDTGROUP_FILE_NAME_MAX		(MAX_RDTGROUP_TYPE_NAMELEN +	\
@@ -714,7 +712,6 @@ static __init void init_cache_domains(void)
 	struct cpu_cacheinfo *this_cpu_ci;
 	struct cacheinfo *this_leaf;
 	int leaves;
-	char buf[MAX_CPUMASK_CHAR_IN_HEX + 1];
 	unsigned int level;
 
 	for (leaves = 0; leaves < cache_leaves(0); leaves++) {
@@ -725,7 +722,6 @@ static __init void init_cache_domains(void)
 			this_leaf = this_cpu_ci->info_list + leaves;
 			cache_domains[leaves].level = this_leaf->level;
 			mask = &this_leaf->shared_cpu_map;
-			cpumap_print_to_pagebuf(false, buf, mask);
 			for (domain = 0; domain < MAX_CACHE_DOMAINS; domain++) {
 				if (cpumask_test_cpu(cpu,
 				&cache_domains[leaves].shared_cpu_map[domain]))
@@ -753,7 +749,6 @@ DEFINE_SPINLOCK(rdtgroup_task_lock);
 
 void rdtgroup_exit(struct task_struct *tsk)
 {
-
 	spin_lock_irq(&rdtgroup_task_lock);
 	if (!list_empty(&tsk->rg_list)) {
 		struct rdtgroup *rdtgrp = tsk->rdtgroup;
@@ -822,6 +817,29 @@ end:
 	return nbytes;
 }
 
+static void show_rdt_tasks(struct list_head *tasks, struct seq_file *s)
+{
+	struct list_head *pos;
+
+	list_for_each(pos, tasks) {
+		struct task_struct *tsk;
+
+		tsk = list_entry(pos, struct task_struct, rg_list);
+		seq_printf(s, "%d\n", tsk->pid);
+	}
+}
+
+static int rdtgroup_pidlist_show(struct seq_file *s, void *v)
+{
+	struct kernfs_open_file *of = s->private;
+	struct rdtgroup *rdtgrp;
+
+	rdtgrp = rdtgroup_kn_lock_live(of->kn);
+	show_rdt_tasks(&rdtgrp->pset.tasks, s);
+	rdtgroup_kn_unlock(of->kn);
+	return 0;
+}
+
 static struct rftype rdtgroup_partition_base_files[] = {
 	{
 		.name = "tasks",
@@ -861,6 +879,114 @@ static struct rftype rdtgroup_root_base_files[] = {
 	{ }	/* terminate */
 };
 
+/*
+ * Insert task into rdtgrp's tasks with pid in order.
+ */
+static int add_task_in_order(struct task_struct *tsk, struct rdtgroup *rdtgrp)
+{
+	struct list_head *l;
+	struct list_head *start_task = &rdtgrp->pset.tasks;
+
+	if (list_empty(start_task)) {
+		list_add_tail(&tsk->rg_list, start_task);
+		return 0;
+	}
+
+	for (l = start_task->next; l != start_task; l = l->next) {
+		struct task_struct *t;
+
+		t = list_entry(l, struct task_struct, rg_list);
+		WARN_ON(t->pid == tsk->pid);
+		if (t->pid > tsk->pid)
+			break;
+	}
+
+	list_add_tail(&tsk->rg_list, l);
+
+	return 0;
+}
+
+int _rdtgroup_move_task(struct task_struct *tsk, struct rdtgroup *rdtgrp)
+{
+	spin_lock_irq(&rdtgroup_task_lock);
+	list_del_init(&tsk->rg_list);
+
+	add_task_in_order(tsk, rdtgrp);
+
+	tsk->rdtgroup = rdtgrp;
+	spin_unlock_irq(&rdtgroup_task_lock);
+	return 0;
+}
+
+static int rdtgroup_move_task(pid_t pid, struct rdtgroup *rdtgrp,
+			      bool threadgroup, struct kernfs_open_file *of)
+{
+	struct task_struct *tsk;
+	int ret;
+
+	percpu_down_write(&rdtgroup_threadgroup_rwsem);
+	rcu_read_lock();
+	if (pid) {
+		tsk = find_task_by_vpid(pid);
+		if (!tsk) {
+			ret = -ESRCH;
+			goto out_unlock_rcu;
+		}
+	} else {
+		tsk = current;
+	}
+
+	if (threadgroup)
+		tsk = tsk->group_leader;
+
+	get_task_struct(tsk);
+	rcu_read_unlock();
+
+	ret = rdtgroup_procs_write_permission(tsk, of);
+	if (!ret)
+		_rdtgroup_move_task(tsk, rdtgrp);
+
+	put_task_struct(tsk);
+	goto out_unlock_threadgroup;
+
+out_unlock_rcu:
+	rcu_read_unlock();
+out_unlock_threadgroup:
+	percpu_up_write(&rdtgroup_threadgroup_rwsem);
+	return ret;
+}
+
+ssize_t _rdtgroup_procs_write(struct rdtgroup *rdtgrp,
+			   struct kernfs_open_file *of, char *buf,
+			   size_t nbytes, loff_t off, bool threadgroup)
+{
+	pid_t pid;
+	int ret;
+
+	if (kstrtoint(strstrip(buf), 0, &pid) || pid < 0)
+		return -EINVAL;
+
+	ret = rdtgroup_move_task(pid, rdtgrp, threadgroup, of);
+
+	return ret ?: nbytes;
+}
+
+static ssize_t rdtgroup_tasks_write(struct kernfs_open_file *of,
+				  char *buf, size_t nbytes, loff_t off)
+{
+	struct rdtgroup *rdtgrp;
+	int ret;
+
+	rdtgrp = rdtgroup_kn_lock_live(of->kn);
+	if (!rdtgrp)
+		return -ENODEV;
+
+	ret = _rdtgroup_procs_write(rdtgrp, of, buf, nbytes, off, false);
+
+	rdtgroup_kn_unlock(of->kn);
+	return ret;
+}
+
 static void *rdtgroup_idr_replace(struct idr *idr, void *ptr, int id)
 {
 	void *ret;
@@ -1180,7 +1306,7 @@ static void setup_task_rg_lists(struct rdtgroup *rdtgrp, bool enable)
 		spin_lock_irq(&p->sighand->siglock);
 		if (!(p->flags & PF_EXITING)) {
 			if (enable) {
-				list_add_tail(&p->rg_list, &rdtgrp->pset.tasks);
+				add_task_in_order(p, rdtgrp);
 				p->rdtgroup = rdtgrp;
 				atomic_inc(&rdtgrp->pset.refcount);
 			} else {
-- 
2.5.0