slub: Add statistics for this_cmpxchg_double failures

Add some statistics for debugging.

Signed-off-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Pekka Enberg <penberg@kernel.org>

2 files changed, 3 insertions, 1 deletions

diff --git a/include/linux/slub_def.h b/include/linux/slub_def.h
index 90fbb6d87e11..45ca123e8002 100644
--- a/include/linux/slub_def.h
+++ b/include/linux/slub_def.h
@@ -32,6 +32,7 @@ enum stat_item {
         DEACTIVATE_TO_TAIL,     /* Cpu slab was moved to the tail of partials */
         DEACTIVATE_REMOTE_FREES,/* Slab contained remotely freed objects */
         ORDER_FALLBACK,         /* Number of times fallback was necessary */
+        CMPXCHG_DOUBLE_CPU_FAIL,/* Failure of this_cpu_cmpxchg_double */
         NR_SLUB_STAT_ITEMS };
 
 struct kmem_cache_cpu {
diff --git a/mm/slub.c b/mm/slub.c
index e126cfbd3df2..93de30db95f5 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -217,7 +217,7 @@ static inline void sysfs_slab_remove(struct kmem_cache *s)
 
 #endif
 
-static inline void stat(struct kmem_cache *s, enum stat_item si)
+static inline void stat(const struct kmem_cache *s, enum stat_item si)
 {
 #ifdef CONFIG_SLUB_STATS
         __this_cpu_inc(s->cpu_slab->stat[si]);
@@ -1597,6 +1597,7 @@ static inline void note_cmpxchg_failure(const char *n,
                 printk("for unknown reason: actual=%lx was=%lx target=%lx\n",
                         actual_tid, tid, next_tid(tid));
 #endif
+        stat(s, CMPXCHG_DOUBLE_CPU_FAIL);
 }
 
 #endif