From d3b553bd71657390426dc25138482d9ea17279b1 Mon Sep 17 00:00:00 2001
From: Thomas Gleixner <tglx@linutronix.de>
Date: Thu, 25 Oct 2012 10:32:35 +0100
Subject: [PATCH 172/518] mm: Enable SLUB for RT

Make SLUB RT aware by converting locks to raw and using free lists to
move the freeing out of the lock held region.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 mm/slab.h |   4 ++
 mm/slub.c | 136 ++++++++++++++++++++++++++++++++++++++++++------------
 2 files changed, 110 insertions(+), 30 deletions(-)

diff --git a/mm/slab.h b/mm/slab.h
index 93a2c91f5b43c..98406c0b98047 100644
--- a/mm/slab.h
+++ b/mm/slab.h
@@ -451,7 +451,11 @@ static inline void slab_post_alloc_hook(struct kmem_cache *s, gfp_t flags,
  * The slab lists for all objects.
  */
 struct kmem_cache_node {
+#ifdef CONFIG_SLUB
+	raw_spinlock_t list_lock;
+#else
 	spinlock_t list_lock;
+#endif
 
 #ifdef CONFIG_SLAB
 	struct list_head slabs_partial;	/* partial list first, better asm code */
diff --git a/mm/slub.c b/mm/slub.c
index 1a0c92ee8b993..f84b6c3b861c7 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -1193,7 +1193,7 @@ static noinline int free_debug_processing(
 	unsigned long uninitialized_var(flags);
 	int ret = 0;
 
-	spin_lock_irqsave(&n->list_lock, flags);
+	raw_spin_lock_irqsave(&n->list_lock, flags);
 	slab_lock(page);
 
 	if (s->flags & SLAB_CONSISTENCY_CHECKS) {
@@ -1228,7 +1228,7 @@ static noinline int free_debug_processing(
 			 bulk_cnt, cnt);
 
 	slab_unlock(page);
-	spin_unlock_irqrestore(&n->list_lock, flags);
+	raw_spin_unlock_irqrestore(&n->list_lock, flags);
 	if (!ret)
 		slab_fix(s, "Object at 0x%p not freed", object);
 	return ret;
@@ -1361,6 +1361,12 @@ static bool freelist_corrupted(struct kmem_cache *s, struct page *page,
 }
 #endif /* CONFIG_SLUB_DEBUG */
 
+struct slub_free_list {
+	raw_spinlock_t		lock;
+	struct list_head	list;
+};
+static DEFINE_PER_CPU(struct slub_free_list, slub_free_list);
+
 /*
  * Hooks for other subsystems that check memory allocations. In a typical
  * production configuration these hooks all should produce no code at all.
@@ -1583,7 +1589,11 @@ static struct page *allocate_slab(struct kmem_cache *s, gfp_t flags, int node)
 
 	flags &= gfp_allowed_mask;
 
+#ifdef CONFIG_PREEMPT_RT_FULL
+	if (system_state > SYSTEM_BOOTING)
+#else
 	if (gfpflags_allow_blocking(flags))
+#endif
 		local_irq_enable();
 
 	flags |= s->allocflags;
@@ -1642,7 +1652,11 @@ static struct page *allocate_slab(struct kmem_cache *s, gfp_t flags, int node)
 	page->frozen = 1;
 
 out:
+#ifdef CONFIG_PREEMPT_RT_FULL
+	if (system_state > SYSTEM_BOOTING)
+#else
 	if (gfpflags_allow_blocking(flags))
+#endif
 		local_irq_disable();
 	if (!page)
 		return NULL;
@@ -1700,6 +1714,16 @@ static void __free_slab(struct kmem_cache *s, struct page *page)
 	__free_pages(page, order);
 }
 
+static void free_delayed(struct list_head *h)
+{
+	while(!list_empty(h)) {
+		struct page *page = list_first_entry(h, struct page, lru);
+
+		list_del(&page->lru);
+		__free_slab(page->slab_cache, page);
+	}
+}
+
 #define need_reserve_slab_rcu						\
 	(sizeof(((struct page *)NULL)->lru) < sizeof(struct rcu_head))
 
@@ -1731,6 +1755,12 @@ static void free_slab(struct kmem_cache *s, struct page *page)
 		}
 
 		call_rcu(head, rcu_free_slab);
+	} else if (irqs_disabled()) {
+		struct slub_free_list *f = this_cpu_ptr(&slub_free_list);
+
+		raw_spin_lock(&f->lock);
+		list_add(&page->lru, &f->list);
+		raw_spin_unlock(&f->lock);
 	} else
 		__free_slab(s, page);
 }
@@ -1838,7 +1868,7 @@ static void *get_partial_node(struct kmem_cache *s, struct kmem_cache_node *n,
 	if (!n || !n->nr_partial)
 		return NULL;
 
-	spin_lock(&n->list_lock);
+	raw_spin_lock(&n->list_lock);
 	list_for_each_entry_safe(page, page2, &n->partial, lru) {
 		void *t;
 
@@ -1863,7 +1893,7 @@ static void *get_partial_node(struct kmem_cache *s, struct kmem_cache_node *n,
 			break;
 
 	}
-	spin_unlock(&n->list_lock);
+	raw_spin_unlock(&n->list_lock);
 	return object;
 }
 
@@ -2115,7 +2145,7 @@ static void deactivate_slab(struct kmem_cache *s, struct page *page,
 			 * that acquire_slab() will see a slab page that
 			 * is frozen
 			 */
-			spin_lock(&n->list_lock);
+			raw_spin_lock(&n->list_lock);
 		}
 	} else {
 		m = M_FULL;
@@ -2126,7 +2156,7 @@ static void deactivate_slab(struct kmem_cache *s, struct page *page,
 			 * slabs from diagnostic functions will not see
 			 * any frozen slabs.
 			 */
-			spin_lock(&n->list_lock);
+			raw_spin_lock(&n->list_lock);
 		}
 	}
 
@@ -2161,7 +2191,7 @@ static void deactivate_slab(struct kmem_cache *s, struct page *page,
 		goto redo;
 
 	if (lock)
-		spin_unlock(&n->list_lock);
+		raw_spin_unlock(&n->list_lock);
 
 	if (m == M_FREE) {
 		stat(s, DEACTIVATE_EMPTY);
@@ -2197,10 +2227,10 @@ static void unfreeze_partials(struct kmem_cache *s,
 		n2 = get_node(s, page_to_nid(page));
 		if (n != n2) {
 			if (n)
-				spin_unlock(&n->list_lock);
+				raw_spin_unlock(&n->list_lock);
 
 			n = n2;
-			spin_lock(&n->list_lock);
+			raw_spin_lock(&n->list_lock);
 		}
 
 		do {
@@ -2229,7 +2259,7 @@ static void unfreeze_partials(struct kmem_cache *s,
 	}
 
 	if (n)
-		spin_unlock(&n->list_lock);
+		raw_spin_unlock(&n->list_lock);
 
 	while (discard_page) {
 		page = discard_page;
@@ -2268,14 +2298,21 @@ static void put_cpu_partial(struct kmem_cache *s, struct page *page, int drain)
 			pobjects = oldpage->pobjects;
 			pages = oldpage->pages;
 			if (drain && pobjects > s->cpu_partial) {
+				struct slub_free_list *f;
 				unsigned long flags;
+				LIST_HEAD(tofree);
 				/*
 				 * partial array is full. Move the existing
 				 * set to the per node partial list.
 				 */
 				local_irq_save(flags);
 				unfreeze_partials(s, this_cpu_ptr(s->cpu_slab));
+				f = this_cpu_ptr(&slub_free_list);
+				raw_spin_lock(&f->lock);
+				list_splice_init(&f->list, &tofree);
+				raw_spin_unlock(&f->lock);
 				local_irq_restore(flags);
+				free_delayed(&tofree);
 				oldpage = NULL;
 				pobjects = 0;
 				pages = 0;
@@ -2343,7 +2380,22 @@ static bool has_cpu_slab(int cpu, void *info)
 
 static void flush_all(struct kmem_cache *s)
 {
+	LIST_HEAD(tofree);
+	int cpu;
+
 	on_each_cpu_cond(has_cpu_slab, flush_cpu_slab, s, 1, GFP_ATOMIC);
+	for_each_online_cpu(cpu) {
+		struct slub_free_list *f;
+
+		if (!has_cpu_slab(cpu, s))
+			continue;
+
+		f = &per_cpu(slub_free_list, cpu);
+		raw_spin_lock_irq(&f->lock);
+		list_splice_init(&f->list, &tofree);
+		raw_spin_unlock_irq(&f->lock);
+		free_delayed(&tofree);
+	}
 }
 
 /*
@@ -2398,10 +2450,10 @@ static unsigned long count_partial(struct kmem_cache_node *n,
 	unsigned long x = 0;
 	struct page *page;
 
-	spin_lock_irqsave(&n->list_lock, flags);
+	raw_spin_lock_irqsave(&n->list_lock, flags);
 	list_for_each_entry(page, &n->partial, lru)
 		x += get_count(page);
-	spin_unlock_irqrestore(&n->list_lock, flags);
+	raw_spin_unlock_irqrestore(&n->list_lock, flags);
 	return x;
 }
 #endif /* CONFIG_SLUB_DEBUG || CONFIG_SYSFS */
@@ -2539,8 +2591,10 @@ static inline void *get_freelist(struct kmem_cache *s, struct page *page)
  * already disabled (which is the case for bulk allocation).
  */
 static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node,
-			  unsigned long addr, struct kmem_cache_cpu *c)
+			  unsigned long addr, struct kmem_cache_cpu *c,
+			  struct list_head *to_free)
 {
+	struct slub_free_list *f;
 	void *freelist;
 	struct page *page;
 
@@ -2607,6 +2661,13 @@ static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node,
 	VM_BUG_ON(!c->page->frozen);
 	c->freelist = get_freepointer(s, freelist);
 	c->tid = next_tid(c->tid);
+
+out:
+	f = this_cpu_ptr(&slub_free_list);
+	raw_spin_lock(&f->lock);
+	list_splice_init(&f->list, to_free);
+	raw_spin_unlock(&f->lock);
+
 	return freelist;
 
 new_slab:
@@ -2622,7 +2683,7 @@ static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node,
 
 	if (unlikely(!freelist)) {
 		slab_out_of_memory(s, gfpflags, node);
-		return NULL;
+		goto out;
 	}
 
 	page = c->page;
@@ -2635,7 +2696,7 @@ static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node,
 		goto new_slab;	/* Slab failed checks. Next slab needed */
 
 	deactivate_slab(s, page, get_freepointer(s, freelist), c);
-	return freelist;
+	goto out;
 }
 
 /*
@@ -2647,6 +2708,7 @@ static void *__slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node,
 {
 	void *p;
 	unsigned long flags;
+	LIST_HEAD(tofree);
 
 	local_irq_save(flags);
 #ifdef CONFIG_PREEMPT
@@ -2658,8 +2720,9 @@ static void *__slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node,
 	c = this_cpu_ptr(s->cpu_slab);
 #endif
 
-	p = ___slab_alloc(s, gfpflags, node, addr, c);
+	p = ___slab_alloc(s, gfpflags, node, addr, c, &tofree);
 	local_irq_restore(flags);
+	free_delayed(&tofree);
 	return p;
 }
 
@@ -2845,7 +2908,7 @@ static void __slab_free(struct kmem_cache *s, struct page *page,
 
 	do {
 		if (unlikely(n)) {
-			spin_unlock_irqrestore(&n->list_lock, flags);
+			raw_spin_unlock_irqrestore(&n->list_lock, flags);
 			n = NULL;
 		}
 		prior = page->freelist;
@@ -2877,7 +2940,7 @@ static void __slab_free(struct kmem_cache *s, struct page *page,
 				 * Otherwise the list_lock will synchronize with
 				 * other processors updating the list of slabs.
 				 */
-				spin_lock_irqsave(&n->list_lock, flags);
+				raw_spin_lock_irqsave(&n->list_lock, flags);
 
 			}
 		}
@@ -2919,7 +2982,7 @@ static void __slab_free(struct kmem_cache *s, struct page *page,
 		add_partial(n, page, DEACTIVATE_TO_TAIL);
 		stat(s, FREE_ADD_PARTIAL);
 	}
-	spin_unlock_irqrestore(&n->list_lock, flags);
+	raw_spin_unlock_irqrestore(&n->list_lock, flags);
 	return;
 
 slab_empty:
@@ -2934,7 +2997,7 @@ static void __slab_free(struct kmem_cache *s, struct page *page,
 		remove_full(s, n, page);
 	}
 
-	spin_unlock_irqrestore(&n->list_lock, flags);
+	raw_spin_unlock_irqrestore(&n->list_lock, flags);
 	stat(s, FREE_SLAB);
 	discard_slab(s, page);
 }
@@ -3141,6 +3204,7 @@ int kmem_cache_alloc_bulk(struct kmem_cache *s, gfp_t flags, size_t size,
 			  void **p)
 {
 	struct kmem_cache_cpu *c;
+	LIST_HEAD(to_free);
 	int i;
 
 	/* memcg and kmem_cache debug support */
@@ -3173,7 +3237,7 @@ int kmem_cache_alloc_bulk(struct kmem_cache *s, gfp_t flags, size_t size,
 			 * of re-populating per CPU c->freelist
 			 */
 			p[i] = ___slab_alloc(s, flags, NUMA_NO_NODE,
-					    _RET_IP_, c);
+					    _RET_IP_, c, &to_free);
 			if (unlikely(!p[i]))
 				goto error;
 
@@ -3185,6 +3249,7 @@ int kmem_cache_alloc_bulk(struct kmem_cache *s, gfp_t flags, size_t size,
 	}
 	c->tid = next_tid(c->tid);
 	local_irq_enable();
+	free_delayed(&to_free);
 
 	/* Clear memory outside IRQ disabled fastpath loop */
 	if (unlikely(flags & __GFP_ZERO)) {
@@ -3332,7 +3397,7 @@ static void
 init_kmem_cache_node(struct kmem_cache_node *n)
 {
 	n->nr_partial = 0;
-	spin_lock_init(&n->list_lock);
+	raw_spin_lock_init(&n->list_lock);
 	INIT_LIST_HEAD(&n->partial);
 #ifdef CONFIG_SLUB_DEBUG
 	atomic_long_set(&n->nr_slabs, 0);
@@ -3686,6 +3751,10 @@ static void list_slab_objects(struct kmem_cache *s, struct page *page,
 							const char *text)
 {
 #ifdef CONFIG_SLUB_DEBUG
+#ifdef CONFIG_PREEMPT_RT_BASE
+	/* XXX move out of irq-off section */
+	slab_err(s, page, text, s->name);
+#else
 	void *addr = page_address(page);
 	void *p;
 	unsigned long *map = kzalloc(BITS_TO_LONGS(page->objects) *
@@ -3706,6 +3775,7 @@ static void list_slab_objects(struct kmem_cache *s, struct page *page,
 	slab_unlock(page);
 	kfree(map);
 #endif
+#endif
 }
 
 /*
@@ -3719,7 +3789,7 @@ static void free_partial(struct kmem_cache *s, struct kmem_cache_node *n)
 	struct page *page, *h;
 
 	BUG_ON(irqs_disabled());
-	spin_lock_irq(&n->list_lock);
+	raw_spin_lock_irq(&n->list_lock);
 	list_for_each_entry_safe(page, h, &n->partial, lru) {
 		if (!page->inuse) {
 			remove_partial(n, page);
@@ -3729,7 +3799,7 @@ static void free_partial(struct kmem_cache *s, struct kmem_cache_node *n)
 			"Objects remaining in %s on __kmem_cache_shutdown()");
 		}
 	}
-	spin_unlock_irq(&n->list_lock);
+	raw_spin_unlock_irq(&n->list_lock);
 
 	list_for_each_entry_safe(page, h, &discard, lru)
 		discard_slab(s, page);
@@ -3973,7 +4043,7 @@ int __kmem_cache_shrink(struct kmem_cache *s)
 		for (i = 0; i < SHRINK_PROMOTE_MAX; i++)
 			INIT_LIST_HEAD(promote + i);
 
-		spin_lock_irqsave(&n->list_lock, flags);
+		raw_spin_lock_irqsave(&n->list_lock, flags);
 
 		/*
 		 * Build lists of slabs to discard or promote.
@@ -4004,7 +4074,7 @@ int __kmem_cache_shrink(struct kmem_cache *s)
 		for (i = SHRINK_PROMOTE_MAX - 1; i >= 0; i--)
 			list_splice(promote + i, &n->partial);
 
-		spin_unlock_irqrestore(&n->list_lock, flags);
+		raw_spin_unlock_irqrestore(&n->list_lock, flags);
 
 		/* Release empty slabs */
 		list_for_each_entry_safe(page, t, &discard, lru)
@@ -4217,6 +4287,12 @@ void __init kmem_cache_init(void)
 {
 	static __initdata struct kmem_cache boot_kmem_cache,
 		boot_kmem_cache_node;
+	int cpu;
+
+	for_each_possible_cpu(cpu) {
+		raw_spin_lock_init(&per_cpu(slub_free_list, cpu).lock);
+		INIT_LIST_HEAD(&per_cpu(slub_free_list, cpu).list);
+	}
 
 	if (debug_guardpage_minorder())
 		slub_max_order = 0;
@@ -4425,7 +4501,7 @@ static int validate_slab_node(struct kmem_cache *s,
 	struct page *page;
 	unsigned long flags;
 
-	spin_lock_irqsave(&n->list_lock, flags);
+	raw_spin_lock_irqsave(&n->list_lock, flags);
 
 	list_for_each_entry(page, &n->partial, lru) {
 		validate_slab_slab(s, page, map);
@@ -4447,7 +4523,7 @@ static int validate_slab_node(struct kmem_cache *s,
 		       s->name, count, atomic_long_read(&n->nr_slabs));
 
 out:
-	spin_unlock_irqrestore(&n->list_lock, flags);
+	raw_spin_unlock_irqrestore(&n->list_lock, flags);
 	return count;
 }
 
@@ -4635,12 +4711,12 @@ static int list_locations(struct kmem_cache *s, char *buf,
 		if (!atomic_long_read(&n->nr_slabs))
 			continue;
 
-		spin_lock_irqsave(&n->list_lock, flags);
+		raw_spin_lock_irqsave(&n->list_lock, flags);
 		list_for_each_entry(page, &n->partial, lru)
 			process_slab(&t, s, page, alloc, map);
 		list_for_each_entry(page, &n->full, lru)
 			process_slab(&t, s, page, alloc, map);
-		spin_unlock_irqrestore(&n->list_lock, flags);
+		raw_spin_unlock_irqrestore(&n->list_lock, flags);
 	}
 
 	for (i = 0; i < t.count; i++) {
-- 
2.41.0

