[PATCH v4 17/22] slab: remove unused PREEMPT_RT specific macros

Vlastimil Babka
2026-01-23T06:54:06Z

The macros slub_get_cpu_ptr()/slub_put_cpu_ptr() are now unused, remove
them. USE_LOCKLESS_FAST_PATH() has lost its true meaning with the code
being removed. The only remaining usage is in fact testing whether we
can assert irqs disabled, because spin_lock_irqsave() only does that on
!RT. Test for CONFIG_PREEMPT_RT instead.

Reviewed-by: Hao Li <hao.li@linux.dev>
Reviewed-by: Suren Baghdasaryan <surenb@google.com>
Reviewed-by: Harry Yoo <harry.yoo@oracle.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
---
mm/slub.c | 24 +-----------------------
1 file changed, 1 insertion(+), 23 deletions(-)

diff --git a/mm/slub.c b/mm/slub.c
index 8ecd5766635b..1d135baf5e9e 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -201,28 +201,6 @@ enum slab_flags {
SL_pfmemalloc = PG_active, /* Historical reasons for this bit */
};

-/*
- * We could simply use migrate_disable()/enable() but as long as it's a
- * function call even on !PREEMPT_RT, use inline preempt_disable() there.
- */
-#ifndef CONFIG_PREEMPT_RT
-#define slub_get_cpu_ptr(var) get_cpu_ptr(var)
-#define slub_put_cpu_ptr(var) put_cpu_ptr(var)
-#define USE_LOCKLESS_FAST_PATH() (true)
-#else
-#define slub_get_cpu_ptr(var) \
-({ \
- migrate_disable(); \
- this_cpu_ptr(var); \
-})
-#define slub_put_cpu_ptr(var) \
-do { \
- (void)(var); \
- migrate_enable(); \
-} while (0)
-#define USE_LOCKLESS_FAST_PATH() (false)
-#endif
-
#ifndef CONFIG_SLUB_TINY
#define __fastpath_inline __always_inline
#else
@@ -713,7 +691,7 @@ static inline bool __slab_update_freelist(struct kmem_cache *s, struct slab *sla
{
bool ret;

- if (USE_LOCKLESS_FAST_PATH())
+ if (!IS_ENABLED(CONFIG_PREEMPT_RT))
lockdep_assert_irqs_disabled();

if (s->flags & __CMPXCHG_DOUBLE)

--
2.52.0