Merge tag 'locking-core-2023-06-27' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull locking updates from Ingo Molnar:

 - Introduce cmpxchg128() -- aka. the demise of cmpxchg_double()

   The cmpxchg128() family of functions is basically & functionally the
   same as cmpxchg_double(), but with a saner interface.

   Instead of a 6-parameter horror that forced u128 - u64/u64-halves
   layout details on the interface and exposed users to complexity,
   fragility & bugs, use a natural 3-parameter interface with u128
   types.

 - Restructure the generated atomic headers, and add kerneldoc comments
   for all of the generic atomic{,64,_long}_t operations.

   The generated definitions are much cleaner now, and come with
   documentation.

 - Implement lock_set_cmp_fn() on lockdep, for defining an ordering when
   taking multiple locks of the same type.

   This gets rid of one use of lockdep_set_novalidate_class() in the
   bcache code.

 - Fix raw_cpu_generic_try_cmpxchg() bug due to an unintended variable
   shadowing generating garbage code on Clang on certain ARM builds.

* tag 'locking-core-2023-06-27' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (43 commits)
  locking/atomic: scripts: fix ${atomic}_dec_if_positive() kerneldoc
  percpu: Fix self-assignment of __old in raw_cpu_generic_try_cmpxchg()
  locking/atomic: treewide: delete arch_atomic_*() kerneldoc
  locking/atomic: docs: Add atomic operations to the driver basic API documentation
  locking/atomic: scripts: generate kerneldoc comments
  docs: scripts: kernel-doc: accept bitwise negation like ~@var
  locking/atomic: scripts: simplify raw_atomic*() definitions
  locking/atomic: scripts: simplify raw_atomic_long*() definitions
  locking/atomic: scripts: split pfx/name/sfx/order
  locking/atomic: scripts: restructure fallback ifdeffery
  locking/atomic: scripts: build raw_atomic_long*() directly
  locking/atomic: treewide: use raw_atomic*_<op>()
  locking/atomic: scripts: add trivial raw_atomic*_<op>()
  locking/atomic: scripts: factor out order template generation
  locking/atomic: scripts: remove leftover "${mult}"
  locking/atomic: scripts: remove bogus order parameter
  locking/atomic: xtensa: add preprocessor symbols
  locking/atomic: x86: add preprocessor symbols
  locking/atomic: sparc: add preprocessor symbols
  locking/atomic: sh: add preprocessor symbols
  ...

2 files changed, 128 insertions, 64 deletions

diff --git a/mm/slab.h b/mm/slab.h
index f01ac256a8f5..bc36edd5ba4f 100644
--- a/mm/slab.h
+++ b/mm/slab.h
@@ -6,6 +6,38 @@
  */
 void __init kmem_cache_init(void);
 
+#ifdef CONFIG_64BIT
+# ifdef system_has_cmpxchg128
+# define system_has_freelist_aba()	system_has_cmpxchg128()
+# define try_cmpxchg_freelist		try_cmpxchg128
+# endif
+#define this_cpu_try_cmpxchg_freelist	this_cpu_try_cmpxchg128
+typedef u128 freelist_full_t;
+#else /* CONFIG_64BIT */
+# ifdef system_has_cmpxchg64
+# define system_has_freelist_aba()	system_has_cmpxchg64()
+# define try_cmpxchg_freelist		try_cmpxchg64
+# endif
+#define this_cpu_try_cmpxchg_freelist	this_cpu_try_cmpxchg64
+typedef u64 freelist_full_t;
+#endif /* CONFIG_64BIT */
+
+#if defined(system_has_freelist_aba) && !defined(CONFIG_HAVE_ALIGNED_STRUCT_PAGE)
+#undef system_has_freelist_aba
+#endif
+
+/*
+ * Freelist pointer and counter to cmpxchg together, avoids the typical ABA
+ * problems with cmpxchg of just a pointer.
+ */
+typedef union {
+	struct {
+		void *freelist;
+		unsigned long counter;
+	};
+	freelist_full_t full;
+} freelist_aba_t;
+
 /* Reuses the bits in struct page */
 struct slab {
 	unsigned long __page_flags;
@@ -38,14 +70,21 @@ struct slab {
 #endif
 			};
 			/* Double-word boundary */
-			void *freelist;		/* first free object */
 			union {
-				unsigned long counters;
 				struct {
-					unsigned inuse:16;
-					unsigned objects:15;
-					unsigned frozen:1;
+					void *freelist;		/* first free object */
+					union {
+						unsigned long counters;
+						struct {
+							unsigned inuse:16;
+							unsigned objects:15;
+							unsigned frozen:1;
+						};
+					};
 				};
+#ifdef system_has_freelist_aba
+				freelist_aba_t freelist_counter;
+#endif
 			};
 		};
 		struct rcu_head rcu_head;
@@ -72,8 +111,8 @@ SLAB_MATCH(memcg_data, memcg_data);
 #endif
 #undef SLAB_MATCH
 static_assert(sizeof(struct slab) <= sizeof(struct page));
-#if defined(CONFIG_HAVE_CMPXCHG_DOUBLE) && defined(CONFIG_SLUB)
-static_assert(IS_ALIGNED(offsetof(struct slab, freelist), 2*sizeof(void *)));
+#if defined(system_has_freelist_aba) && defined(CONFIG_SLUB)
+static_assert(IS_ALIGNED(offsetof(struct slab, freelist), sizeof(freelist_aba_t)));
 #endif
 
 /**
diff --git a/mm/slub.c b/mm/slub.c
index c87628cd8a9a..7529626bbec2 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -292,7 +292,12 @@ static inline bool kmem_cache_has_cpu_partial(struct kmem_cache *s)
 /* Poison object */
 #define __OBJECT_POISON		((slab_flags_t __force)0x80000000U)
 /* Use cmpxchg_double */
+
+#ifdef system_has_freelist_aba
 #define __CMPXCHG_DOUBLE	((slab_flags_t __force)0x40000000U)
+#else
+#define __CMPXCHG_DOUBLE	((slab_flags_t __force)0U)
+#endif
 
 /*
  * Tracking user of a slab.
@@ -512,6 +517,40 @@ static __always_inline void slab_unlock(struct slab *slab)
 	__bit_spin_unlock(PG_locked, &page->flags);
 }
 
+static inline bool
+__update_freelist_fast(struct slab *slab,
+		      void *freelist_old, unsigned long counters_old,
+		      void *freelist_new, unsigned long counters_new)
+{
+#ifdef system_has_freelist_aba
+	freelist_aba_t old = { .freelist = freelist_old, .counter = counters_old };
+	freelist_aba_t new = { .freelist = freelist_new, .counter = counters_new };
+
+	return try_cmpxchg_freelist(&slab->freelist_counter.full, &old.full, new.full);
+#else
+	return false;
+#endif
+}
+
+static inline bool
+__update_freelist_slow(struct slab *slab,
+		      void *freelist_old, unsigned long counters_old,
+		      void *freelist_new, unsigned long counters_new)
+{
+	bool ret = false;
+
+	slab_lock(slab);
+	if (slab->freelist == freelist_old &&
+	    slab->counters == counters_old) {
+		slab->freelist = freelist_new;
+		slab->counters = counters_new;
+		ret = true;
+	}
+	slab_unlock(slab);
+
+	return ret;
+}
+
 /*
  * Interrupts must be disabled (for the fallback code to work right), typically
  * by an _irqsave() lock variant. On PREEMPT_RT the preempt_disable(), which is
@@ -519,33 +558,25 @@ static __always_inline void slab_unlock(struct slab *slab)
  * allocation/ free operation in hardirq context. Therefore nothing can
  * interrupt the operation.
  */
-static inline bool __cmpxchg_double_slab(struct kmem_cache *s, struct slab *slab,
+static inline bool __slab_update_freelist(struct kmem_cache *s, struct slab *slab,
 		void *freelist_old, unsigned long counters_old,
 		void *freelist_new, unsigned long counters_new,
 		const char *n)
 {
+	bool ret;
+
 	if (USE_LOCKLESS_FAST_PATH())
 		lockdep_assert_irqs_disabled();
-#if defined(CONFIG_HAVE_CMPXCHG_DOUBLE) && \
-    defined(CONFIG_HAVE_ALIGNED_STRUCT_PAGE)
+
 	if (s->flags & __CMPXCHG_DOUBLE) {
-		if (cmpxchg_double(&slab->freelist, &slab->counters,
-				   freelist_old, counters_old,
-				   freelist_new, counters_new))
-			return true;
-	} else
-#endif
-	{
-		slab_lock(slab);
-		if (slab->freelist == freelist_old &&
-					slab->counters == counters_old) {
-			slab->freelist = freelist_new;
-			slab->counters = counters_new;
-			slab_unlock(slab);
-			return true;
-		}
-		slab_unlock(slab);
+		ret = __update_freelist_fast(slab, freelist_old, counters_old,
+				            freelist_new, counters_new);
+	} else {
+		ret = __update_freelist_slow(slab, freelist_old, counters_old,
+				            freelist_new, counters_new);
 	}
+	if (likely(ret))
+		return true;
 
 	cpu_relax();
 	stat(s, CMPXCHG_DOUBLE_FAIL);
@@ -557,36 +588,26 @@ static inline bool __cmpxchg_double_slab(struct kmem_cache *s, struct slab *slab
 	return false;
 }
 
-static inline bool cmpxchg_double_slab(struct kmem_cache *s, struct slab *slab,
+static inline bool slab_update_freelist(struct kmem_cache *s, struct slab *slab,
 		void *freelist_old, unsigned long counters_old,
 		void *freelist_new, unsigned long counters_new,
 		const char *n)
 {
-#if defined(CONFIG_HAVE_CMPXCHG_DOUBLE) && \
-    defined(CONFIG_HAVE_ALIGNED_STRUCT_PAGE)
+	bool ret;
+
 	if (s->flags & __CMPXCHG_DOUBLE) {
-		if (cmpxchg_double(&slab->freelist, &slab->counters,
-				   freelist_old, counters_old,
-				   freelist_new, counters_new))
-			return true;
-	} else
-#endif
-	{
+		ret = __update_freelist_fast(slab, freelist_old, counters_old,
+				            freelist_new, counters_new);
+	} else {
 		unsigned long flags;
 
 		local_irq_save(flags);
-		slab_lock(slab);
-		if (slab->freelist == freelist_old &&
-					slab->counters == counters_old) {
-			slab->freelist = freelist_new;
-			slab->counters = counters_new;
-			slab_unlock(slab);
-			local_irq_restore(flags);
-			return true;
-		}
-		slab_unlock(slab);
+		ret = __update_freelist_slow(slab, freelist_old, counters_old,
+				            freelist_new, counters_new);
 		local_irq_restore(flags);
 	}
+	if (likely(ret))
+		return true;
 
 	cpu_relax();
 	stat(s, CMPXCHG_DOUBLE_FAIL);
@@ -2228,7 +2249,7 @@ static inline void *acquire_slab(struct kmem_cache *s,
 	VM_BUG_ON(new.frozen);
 	new.frozen = 1;
 
-	if (!__cmpxchg_double_slab(s, slab,
+	if (!__slab_update_freelist(s, slab,
 			freelist, counters,
 			new.freelist, new.counters,
 			"acquire_slab"))
@@ -2554,7 +2575,7 @@ redo:
 	}
 
 
-	if (!cmpxchg_double_slab(s, slab,
+	if (!slab_update_freelist(s, slab,
 				old.freelist, old.counters,
 				new.freelist, new.counters,
 				"unfreezing slab")) {
@@ -2611,7 +2632,7 @@ static void __unfreeze_partials(struct kmem_cache *s, struct slab *partial_slab)
 
 			new.frozen = 0;
 
-		} while (!__cmpxchg_double_slab(s, slab,
+		} while (!__slab_update_freelist(s, slab,
 				old.freelist, old.counters,
 				new.freelist, new.counters,
 				"unfreezing slab"));
@@ -3008,6 +3029,18 @@ static inline bool pfmemalloc_match(struct slab *slab, gfp_t gfpflags)
 }
 
 #ifndef CONFIG_SLUB_TINY
+static inline bool
+__update_cpu_freelist_fast(struct kmem_cache *s,
+			   void *freelist_old, void *freelist_new,
+			   unsigned long tid)
+{
+	freelist_aba_t old = { .freelist = freelist_old, .counter = tid };
+	freelist_aba_t new = { .freelist = freelist_new, .counter = next_tid(tid) };
+
+	return this_cpu_try_cmpxchg_freelist(s->cpu_slab->freelist_tid.full,
+					     &old.full, new.full);
+}
+
 /*
  * Check the slab->freelist and either transfer the freelist to the
  * per cpu freelist or deactivate the slab.
@@ -3034,7 +3067,7 @@ static inline void *get_freelist(struct kmem_cache *s, struct slab *slab)
 		new.inuse = slab->objects;
 		new.frozen = freelist != NULL;
 
-	} while (!__cmpxchg_double_slab(s, slab,
+	} while (!__slab_update_freelist(s, slab,
 		freelist, counters,
 		NULL, new.counters,
 		"get_freelist"));
@@ -3359,11 +3392,7 @@ redo:
 		 * against code executing on this cpu *not* from access by
 		 * other cpus.
 		 */
-		if (unlikely(!this_cpu_cmpxchg_double(
-				s->cpu_slab->freelist, s->cpu_slab->tid,
-				object, tid,
-				next_object, next_tid(tid)))) {
-
+		if (unlikely(!__update_cpu_freelist_fast(s, object, next_object, tid))) {
 			note_cmpxchg_failure("slab_alloc", s, tid);
 			goto redo;
 		}
@@ -3631,7 +3660,7 @@ static void __slab_free(struct kmem_cache *s, struct slab *slab,
 			}
 		}
 
-	} while (!cmpxchg_double_slab(s, slab,
+	} while (!slab_update_freelist(s, slab,
 		prior, counters,
 		head, new.counters,
 		"__slab_free"));
@@ -3736,11 +3765,7 @@ redo:
 
 		set_freepointer(s, tail_obj, freelist);
 
-		if (unlikely(!this_cpu_cmpxchg_double(
-				s->cpu_slab->freelist, s->cpu_slab->tid,
-				freelist, tid,
-				head, next_tid(tid)))) {
-
+		if (unlikely(!__update_cpu_freelist_fast(s, freelist, head, tid))) {
 			note_cmpxchg_failure("slab_free", s, tid);
 			goto redo;
 		}
@@ -4505,11 +4530,11 @@ static int kmem_cache_open(struct kmem_cache *s, slab_flags_t flags)
 		}
 	}
 
-#if defined(CONFIG_HAVE_CMPXCHG_DOUBLE) && \
-    defined(CONFIG_HAVE_ALIGNED_STRUCT_PAGE)
-	if (system_has_cmpxchg_double() && (s->flags & SLAB_NO_CMPXCHG) == 0)
+#ifdef system_has_freelist_aba
+	if (system_has_freelist_aba() && !(s->flags & SLAB_NO_CMPXCHG)) {
 		/* Enable fast mode */
 		s->flags |= __CMPXCHG_DOUBLE;
+	}
 #endif
 
 	/*