---

yaml
---
r: 142541
b: refs/heads/master
c: a56ed66
h: refs/heads/master
i:
  142539: cfc954d
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 9133df726fdd3df0ca9efcaaae22442198851d65
+refs/heads/master: a56ed663047fc9927ec8b35750d23ece54f85dc7

trunk/mm/pdflush.c

@@ -98,7 +98,6 @@ static int __pdflush(struct pdflush_work *my_work)
 	INIT_LIST_HEAD(&my_work->list);
 
 	spin_lock_irq(&pdflush_lock);
-	nr_pdflush_threads++;
 	for ( ; ; ) {
 		struct pdflush_work *pdf;
 
@@ -126,20 +125,26 @@ static int __pdflush(struct pdflush_work *my_work)
 
 		(*my_work->fn)(my_work->arg0);
 
+		spin_lock_irq(&pdflush_lock);
+
 		/*
 		 * Thread creation: For how long have there been zero
 		 * available threads?
+		 *
+		 * To throttle creation, we reset last_empty_jifs.
 		 */
 		if (time_after(jiffies, last_empty_jifs + 1 * HZ)) {
-			/* unlocked list_empty() test is OK here */
 			if (list_empty(&pdflush_list)) {
-				/* unlocked test is OK here */
-				if (nr_pdflush_threads < MAX_PDFLUSH_THREADS)
+				if (nr_pdflush_threads < MAX_PDFLUSH_THREADS) {
+					last_empty_jifs = jiffies;
+					nr_pdflush_threads++;
+					spin_unlock_irq(&pdflush_lock);
 					start_one_pdflush_thread();
+					spin_lock_irq(&pdflush_lock);
+				}
 			}
 		}
 
-		spin_lock_irq(&pdflush_lock);
 		my_work->fn = NULL;
 
 		/*
@@ -236,13 +241,26 @@ int pdflush_operation(void (*fn)(unsigned long), unsigned long arg0)
 
 static void start_one_pdflush_thread(void)
 {
-	kthread_run(pdflush, NULL, "pdflush");
+	struct task_struct *k;
+
+	k = kthread_run(pdflush, NULL, "pdflush");
+	if (unlikely(IS_ERR(k))) {
+		spin_lock_irq(&pdflush_lock);
+		nr_pdflush_threads--;
+		spin_unlock_irq(&pdflush_lock);
+	}
 }
 
 static int __init pdflush_init(void)
 {
 	int i;
 
+	/*
+	 * Pre-set nr_pdflush_threads...  If we fail to create,
+	 * the count will be decremented.
+	 */
+	nr_pdflush_threads = MIN_PDFLUSH_THREADS;
+
 	for (i = 0; i < MIN_PDFLUSH_THREADS; i++)
 		start_one_pdflush_thread();
 	return 0;