diff mbox series

[v3,31/35] mm, slub: optionally save/restore irqs in slab_[un]lock()/

Message ID 20210729132132.19691-32-vbabka@suse.cz (mailing list archive)
State New
Headers show
Series SLUB: reduce irq disabled scope and make it RT compatible | expand

Commit Message

Vlastimil Babka July 29, 2021, 1:21 p.m. UTC 
For PREEMPT_RT we will need to disable irqs for this bit spinlock. As a
preparation, add a flags parameter, and an internal version that takes
additional bool parameter to control irq saving/restoring (the flags
parameter is compile-time unused if the bool is a constant false).

Convert ___cmpxchg_double_slab(), which also comes with the same bool
parameter, to use the internal version.

Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
---
 mm/slub.c | 49 +++++++++++++++++++++++++++++++------------------
 1 file changed, 31 insertions(+), 18 deletions(-)

Comments

Mel Gorman July 29, 2021, 3:43 p.m. UTC | #1 
On Thu, Jul 29, 2021 at 03:21:28PM +0200, Vlastimil Babka wrote:
> For PREEMPT_RT we will need to disable irqs for this bit spinlock. As a
> preparation, add a flags parameter, and an internal version that takes
> additional bool parameter to control irq saving/restoring (the flags
> parameter is compile-time unused if the bool is a constant false).
> 
> Convert ___cmpxchg_double_slab(), which also comes with the same bool
> parameter, to use the internal version.
> 
> Signed-off-by: Vlastimil Babka <vbabka@suse.cz>

On arm64 allmodconfig, the following build warning was new

 In file included from ./include/linux/spinlock.h:54,
                  from ./include/linux/mmzone.h:8,
                  from ./include/linux/gfp.h:6,
                  from ./include/linux/mm.h:10,
                  from mm/slub.c:13:
 mm/slub.c: In function '___cmpxchg_double_slab.isra.0':
 ./include/linux/irqflags.h:177:3: warning: 'flags' may be used uninitialized in this function [-Wmaybe-uninitialized]
   177 |   arch_local_irq_restore(flags);  \
       |   ^~~~~~~~~~~~~~~~~~~~~~
 mm/slub.c:408:17: note: 'flags' was declared here
   408 |   unsigned long flags;
       |                 ^~~~~
 In file included from ./include/linux/string.h:262,
                  from ./include/linux/bitmap.h:10,
                  from ./include/linux/cpumask.h:12,

No idea what's special about arm allmodconfig that confuses the
compiler.
diff mbox series

Patch

diff --git a/mm/slub.c b/mm/slub.c
index 1ee3ef7a1d3b..2496e0add6f2 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -359,16 +359,33 @@  static inline unsigned int oo_objects(struct kmem_cache_order_objects x)
 /*
  * Per slab locking using the pagelock
  */
-static __always_inline void slab_lock(struct page *page)
+static __always_inline void
+__slab_lock(struct page *page, unsigned long *flags, bool disable_irqs)
 {
 	VM_BUG_ON_PAGE(PageTail(page), page);
+	if (disable_irqs)
+		local_irq_save(*flags);
 	bit_spin_lock(PG_locked, &page->flags);
 }
 
-static __always_inline void slab_unlock(struct page *page)
+static __always_inline void
+__slab_unlock(struct page *page, unsigned long *flags, bool disable_irqs)
 {
 	VM_BUG_ON_PAGE(PageTail(page), page);
 	__bit_spin_unlock(PG_locked, &page->flags);
+	if (disable_irqs)
+		local_irq_restore(*flags);
+}
+
+static __always_inline void
+slab_lock(struct page *page, unsigned long *flags)
+{
+	__slab_lock(page, flags, false);
+}
+
+static __always_inline void slab_unlock(struct page *page, unsigned long *flags)
+{
+	__slab_unlock(page, flags, false);
 }
 
 static inline bool ___cmpxchg_double_slab(struct kmem_cache *s, struct page *page,
@@ -390,21 +407,15 @@  static inline bool ___cmpxchg_double_slab(struct kmem_cache *s, struct page *pag
 	{
 		unsigned long flags;
 
-		if (disable_irqs)
-			local_irq_save(flags);
-		slab_lock(page);
+		__slab_lock(page, &flags, disable_irqs);
 		if (page->freelist == freelist_old &&
 					page->counters == counters_old) {
 			page->freelist = freelist_new;
 			page->counters = counters_new;
-			slab_unlock(page);
-			if (disable_irqs)
-				local_irq_restore(flags);
+			__slab_unlock(page, &flags, disable_irqs);
 			return true;
 		}
-		slab_unlock(page);
-		if (disable_irqs)
-			local_irq_restore(flags);
+		__slab_unlock(page, &flags, disable_irqs);
 	}
 
 	cpu_relax();
@@ -1255,11 +1266,11 @@  static noinline int free_debug_processing(
 	struct kmem_cache_node *n = get_node(s, page_to_nid(page));
 	void *object = head;
 	int cnt = 0;
-	unsigned long flags;
+	unsigned long flags, flags2;
 	int ret = 0;
 
 	spin_lock_irqsave(&n->list_lock, flags);
-	slab_lock(page);
+	slab_lock(page, &flags2);
 
 	if (s->flags & SLAB_CONSISTENCY_CHECKS) {
 		if (!check_slab(s, page))
@@ -1292,7 +1303,7 @@  static noinline int free_debug_processing(
 		slab_err(s, page, "Bulk freelist count(%d) invalid(%d)\n",
 			 bulk_cnt, cnt);
 
-	slab_unlock(page);
+	slab_unlock(page, &flags2);
 	spin_unlock_irqrestore(&n->list_lock, flags);
 	if (!ret)
 		slab_fix(s, "Object at 0x%p not freed", object);
@@ -4040,9 +4051,10 @@  static void list_slab_objects(struct kmem_cache *s, struct page *page,
 	void *addr = page_address(page);
 	unsigned long *map;
 	void *p;
+	unsigned long flags;
 
 	slab_err(s, page, text, s->name);
-	slab_lock(page);
+	slab_lock(page, &flags);
 
 	map = get_map(s, page);
 	for_each_object(p, s, addr, page->objects) {
@@ -4053,7 +4065,7 @@  static void list_slab_objects(struct kmem_cache *s, struct page *page,
 		}
 	}
 	put_map(map);
-	slab_unlock(page);
+	slab_unlock(page, &flags);
 #endif
 }
 
@@ -4784,8 +4796,9 @@  static void validate_slab(struct kmem_cache *s, struct page *page,
 {
 	void *p;
 	void *addr = page_address(page);
+	unsigned long flags;
 
-	slab_lock(page);
+	slab_lock(page, &flags);
 
 	if (!check_slab(s, page) || !on_freelist(s, page, NULL))
 		goto unlock;
@@ -4800,7 +4813,7 @@  static void validate_slab(struct kmem_cache *s, struct page *page,
 			break;
 	}
 unlock:
-	slab_unlock(page);
+	slab_unlock(page, &flags);
 }
 
 static int validate_slab_node(struct kmem_cache *s,