Re: [PATCH] slub: Use the correct per cpu slab on CPU_DEAD

[Christoph Lameter]

On Sat, 27 Oct 2012, Thomas Gleixner wrote:

> Correct this by extending the arguments of unfreeze_partials with the
> target cpu number and use per_cpu_ptr instead of this_cpu_ptr.

Passing the kmem_cache_cpu pointer instead simplifies this a bit and avoid
a per_cpu_ptr operations. That reduces code somewhat and results in no
additional operations for the fast path.


Subject: Use correct cpu_slab on dead cpu

Pass a kmem_cache_cpu pointer into unfreeze partials so that a different
kmem_cache_cpu structure than the local one can be specified.

Reported-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Christoph Lameter <cl@xxxxxxxxx>

Index: linux/mm/slub.c
===================================================================
--- linux.orig/mm/slub.c	2012-10-30 10:23:33.040649727 -0500
+++ linux/mm/slub.c	2012-10-30 10:25:03.401312250 -0500
@@ -1874,10 +1874,10 @@ redo:
  *
  * This function must be called with interrupt disabled.
  */
-static void unfreeze_partials(struct kmem_cache *s)
+static void unfreeze_partials(struct kmem_cache *s,
+		struct kmem_cache_cpu *c)
 {
 	struct kmem_cache_node *n = NULL, *n2 = NULL;
-	struct kmem_cache_cpu *c = this_cpu_ptr(s->cpu_slab);
 	struct page *page, *discard_page = NULL;

 	while ((page = c->partial)) {
@@ -1963,7 +1963,7 @@ static int put_cpu_partial(struct kmem_c
 				 * set to the per node partial list.
 				 */
 				local_irq_save(flags);
-				unfreeze_partials(s);
+				unfreeze_partials(s, this_cpu_ptr(s->cpu_slab));
 				local_irq_restore(flags);
 				oldpage = NULL;
 				pobjects = 0;
@@ -2006,7 +2006,7 @@ static inline void __flush_cpu_slab(stru
 		if (c->page)
 			flush_slab(s, c);

-		unfreeze_partials(s);
+		unfreeze_partials(s, c);
 	}
 }

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