[PATCH] SLAB: Record actual last user of freed objects.

[PATCH] SLAB: Record actual last user of freed objects.

[Suleiman Souhlal]

Currently, when using CONFIG_DEBUG_SLAB, we put in kfree() or
kmem_cache_free() as the last user of free objects, which is not
very useful, so change it to the caller of those functions instead.

Signed-off-by: Suleiman Souhlal <suleiman@google.com>
---
 mm/slab.c |    9 +++++----
 1 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/mm/slab.c b/mm/slab.c
index 98f114d..615e76c 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -3603,13 +3603,14 @@ free_done:
  * Release an obj back to its cache. If the obj has a constructed state, it must
  * be in this state _before_ it is released.  Called with disabled ints.
  */
-static inline void __cache_free(struct kmem_cache *cachep, void *objp)
+static inline void __cache_free(struct kmem_cache *cachep, void *objp,
+    void *caller)
 {
 	struct array_cache *ac = cpu_cache_get(cachep);
 
 	check_irq_off();
 	kmemleak_free_recursive(objp, cachep->flags);
-	objp = cache_free_debugcheck(cachep, objp, __builtin_return_address(0));
+	objp = cache_free_debugcheck(cachep, objp, caller);
 
 	kmemcheck_slab_free(cachep, objp, obj_size(cachep));
 
@@ -3800,7 +3801,7 @@ void kmem_cache_free(struct kmem_cache *cachep, void *objp)
 	debug_check_no_locks_freed(objp, obj_size(cachep));
 	if (!(cachep->flags & SLAB_DEBUG_OBJECTS))
 		debug_check_no_obj_freed(objp, obj_size(cachep));
-	__cache_free(cachep, objp);
+	__cache_free(cachep, objp, __builtin_return_address(0));
 	local_irq_restore(flags);
 
 	trace_kmem_cache_free(_RET_IP_, objp);
@@ -3830,7 +3831,7 @@ void kfree(const void *objp)
 	c = virt_to_cache(objp);
 	debug_check_no_locks_freed(objp, obj_size(c));
 	debug_check_no_obj_freed(objp, obj_size(c));
-	__cache_free(c, (void *)objp);
+	__cache_free(c, (void *)objp, __builtin_return_address(0));
 	local_irq_restore(flags);
 }
 EXPORT_SYMBOL(kfree);
-- 
1.7.3.1

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Re: [PATCH] SLAB: Record actual last user of freed objects.

[David Rientjes]

On Thu, 2 Jun 2011, Suleiman Souhlal wrote:

> Currently, when using CONFIG_DEBUG_SLAB, we put in kfree() or
> kmem_cache_free() as the last user of free objects, which is not
> very useful, so change it to the caller of those functions instead.
> 
> Signed-off-by: Suleiman Souhlal <suleiman@google.com>

Acked-by: David Rientjes <rientjes@google.com>

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Re: [PATCH] SLAB: Record actual last user of freed objects.

[Christoph Lameter]

On Thu, 2 Jun 2011, David Rientjes wrote:

> On Thu, 2 Jun 2011, Suleiman Souhlal wrote:
>
> > Currently, when using CONFIG_DEBUG_SLAB, we put in kfree() or
> > kmem_cache_free() as the last user of free objects, which is not
> > very useful, so change it to the caller of those functions instead.
> >
> > Signed-off-by: Suleiman Souhlal <suleiman@google.com>
>
> Acked-by: David Rientjes <rientjes@google.com>

Well note that this increases the overhead of a hot code path. But slub
does the same

Acked-by: Christoph Lameter <cl@linux.com>

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Re: [PATCH] SLAB: Record actual last user of freed objects.

[Pekka Enberg]

On Fri, Jun 3, 2011 at 5:05 PM, Christoph Lameter <cl@linux.com> wrote:
> On Thu, 2 Jun 2011, David Rientjes wrote:
>
>> On Thu, 2 Jun 2011, Suleiman Souhlal wrote:
>>
>> > Currently, when using CONFIG_DEBUG_SLAB, we put in kfree() or
>> > kmem_cache_free() as the last user of free objects, which is not
>> > very useful, so change it to the caller of those functions instead.
>> >
>> > Signed-off-by: Suleiman Souhlal <suleiman@google.com>
>>
>> Acked-by: David Rientjes <rientjes@google.com>
>
> Well note that this increases the overhead of a hot code path. But slub
> does the same
>
> Acked-by: Christoph Lameter <cl@linux.com>

Applied, thanks!

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