Merge branch 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull locking/atomics update from Thomas Gleixner: "The locking, atomics and memory model brains delivered: - A larger update to the atomics code which reworks the ordering barriers, consolidates the atomic primitives, provides the new atomic64_fetch_add_unless() primitive and cleans up the include hell. - Simplify cmpxchg() instrumentation and add instrumentation for xchg() and cmpxchg_double(). - Updates to the memory model and documentation" * 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (48 commits) locking/atomics: Rework ordering barriers locking/atomics: Instrument cmpxchg_double*() locking/atomics: Instrument xchg() locking/atomics: Simplify cmpxchg() instrumentation locking/atomics/x86: Reduce arch_cmpxchg64*() instrumentation tools/memory-model: Rename litmus tests to comply to norm7 tools/memory-model/Documentation: Fix typo, smb->smp sched/Documentation: Update wake_up() & co. memory-barrier guarantees locking/spinlock, sched/core: Clarify requirements for smp_mb__after_spinlock() sched/core: Use smp_mb() in wake_woken_function() tools/memory-model: Add informal LKMM documentation to MAINTAINERS locking/atomics/Documentation: Describe atomic_set() as a write operation tools/memory-model: Make scripts executable tools/memory-model: Remove ACCESS_ONCE() from model tools/memory-model: Remove ACCESS_ONCE() from recipes locking/memory-barriers.txt/kokr: Update Korean translation to fix broken DMA vs. MMIO ordering example MAINTAINERS: Add Daniel Lustig as an LKMM reviewer tools/memory-model: Fix ISA2+pooncelock+pooncelock+pombonce name tools/memory-model: Add litmus test for full multicopy atomicity locking/refcount: Always allow checked forms ...
2018-08-13 12:23:39 -07:00
parent 1c59477428 fd2efaa4eb
commit de5d1b39ea
77 changed files with 991 additions and 1985 deletions
--- a/include/linux/atomic.h
+++ b/include/linux/atomic.h
@@ -2,6 +2,8 @@
 /* Atomic operations usable in machine independent code */
 #ifndef _LINUX_ATOMIC_H
 #define _LINUX_ATOMIC_H
+#include <linux/types.h>
+
 #include <asm/atomic.h>
 #include <asm/barrier.h>

@@ -36,40 +38,46 @@
 * barriers on top of the relaxed variant. In the case where the relaxed
 * variant is already fully ordered, no additional barriers are needed.
 *
- * Besides, if an arch has a special barrier for acquire/release, it could
- * implement its own __atomic_op_* and use the same framework for building
- * variants
- *
- * If an architecture overrides __atomic_op_acquire() it will probably want
- * to define smp_mb__after_spinlock().
+ * If an architecture overrides __atomic_acquire_fence() it will probably
+ * want to define smp_mb__after_spinlock().
 */
-#ifndef __atomic_op_acquire
+#ifndef __atomic_acquire_fence
+#define __atomic_acquire_fence		smp_mb__after_atomic
+#endif
+
+#ifndef __atomic_release_fence
+#define __atomic_release_fence		smp_mb__before_atomic
+#endif
+
+#ifndef __atomic_pre_full_fence
+#define __atomic_pre_full_fence		smp_mb__before_atomic
+#endif
+
+#ifndef __atomic_post_full_fence
+#define __atomic_post_full_fence	smp_mb__after_atomic
+#endif
+
 #define __atomic_op_acquire(op, args...)				\
 ({									\
 	typeof(op##_relaxed(args)) __ret  = op##_relaxed(args);		\
-	smp_mb__after_atomic();						\
+	__atomic_acquire_fence();					\
 	__ret;								\
 })
-#endif

-#ifndef __atomic_op_release
 #define __atomic_op_release(op, args...)				\
 ({									\
-	smp_mb__before_atomic();					\
+	__atomic_release_fence();					\
 	op##_relaxed(args);						\
 })
-#endif

-#ifndef __atomic_op_fence
 #define __atomic_op_fence(op, args...)					\
 ({									\
 	typeof(op##_relaxed(args)) __ret;				\
-	smp_mb__before_atomic();					\
+	__atomic_pre_full_fence();					\
 	__ret = op##_relaxed(args);					\
-	smp_mb__after_atomic();						\
+	__atomic_post_full_fence();					\
 	__ret;								\
 })
-#endif

 /* atomic_add_return_relaxed */
 #ifndef atomic_add_return_relaxed
@@ -95,11 +103,23 @@
 #endif
 #endif /* atomic_add_return_relaxed */

+#ifndef atomic_inc
+#define atomic_inc(v)			atomic_add(1, (v))
+#endif
+
 /* atomic_inc_return_relaxed */
 #ifndef atomic_inc_return_relaxed
+
+#ifndef atomic_inc_return
+#define atomic_inc_return(v)		atomic_add_return(1, (v))
+#define atomic_inc_return_relaxed(v)	atomic_add_return_relaxed(1, (v))
+#define atomic_inc_return_acquire(v)	atomic_add_return_acquire(1, (v))
+#define atomic_inc_return_release(v)	atomic_add_return_release(1, (v))
+#else /* atomic_inc_return */
 #define  atomic_inc_return_relaxed	atomic_inc_return
 #define  atomic_inc_return_acquire	atomic_inc_return
 #define  atomic_inc_return_release	atomic_inc_return
+#endif /* atomic_inc_return */

 #else /* atomic_inc_return_relaxed */

@@ -143,11 +163,23 @@
 #endif
 #endif /* atomic_sub_return_relaxed */

+#ifndef atomic_dec
+#define atomic_dec(v)			atomic_sub(1, (v))
+#endif
+
 /* atomic_dec_return_relaxed */
 #ifndef atomic_dec_return_relaxed
+
+#ifndef atomic_dec_return
+#define atomic_dec_return(v)		atomic_sub_return(1, (v))
+#define atomic_dec_return_relaxed(v)	atomic_sub_return_relaxed(1, (v))
+#define atomic_dec_return_acquire(v)	atomic_sub_return_acquire(1, (v))
+#define atomic_dec_return_release(v)	atomic_sub_return_release(1, (v))
+#else /* atomic_dec_return */
 #define  atomic_dec_return_relaxed	atomic_dec_return
 #define  atomic_dec_return_acquire	atomic_dec_return
 #define  atomic_dec_return_release	atomic_dec_return
+#endif /* atomic_dec_return */

 #else /* atomic_dec_return_relaxed */

@@ -328,12 +360,22 @@
 #endif
 #endif /* atomic_fetch_and_relaxed */

-#ifdef atomic_andnot
-/* atomic_fetch_andnot_relaxed */
+#ifndef atomic_andnot
+#define atomic_andnot(i, v)		atomic_and(~(int)(i), (v))
+#endif
+
 #ifndef atomic_fetch_andnot_relaxed
-#define atomic_fetch_andnot_relaxed	atomic_fetch_andnot
-#define atomic_fetch_andnot_acquire	atomic_fetch_andnot
-#define atomic_fetch_andnot_release	atomic_fetch_andnot
+
+#ifndef atomic_fetch_andnot
+#define atomic_fetch_andnot(i, v)		atomic_fetch_and(~(int)(i), (v))
+#define atomic_fetch_andnot_relaxed(i, v)	atomic_fetch_and_relaxed(~(int)(i), (v))
+#define atomic_fetch_andnot_acquire(i, v)	atomic_fetch_and_acquire(~(int)(i), (v))
+#define atomic_fetch_andnot_release(i, v)	atomic_fetch_and_release(~(int)(i), (v))
+#else /* atomic_fetch_andnot */
+#define atomic_fetch_andnot_relaxed		atomic_fetch_andnot
+#define atomic_fetch_andnot_acquire		atomic_fetch_andnot
+#define atomic_fetch_andnot_release		atomic_fetch_andnot
+#endif /* atomic_fetch_andnot */

 #else /* atomic_fetch_andnot_relaxed */

@@ -352,7 +394,6 @@
 	__atomic_op_fence(atomic_fetch_andnot, __VA_ARGS__)
 #endif
 #endif /* atomic_fetch_andnot_relaxed */
-#endif /* atomic_andnot */

 /* atomic_fetch_xor_relaxed */
 #ifndef atomic_fetch_xor_relaxed
@@ -519,113 +560,141 @@
 #endif
 #endif /* xchg_relaxed */

+/**
+ * atomic_fetch_add_unless - add unless the number is already a given value
+ * @v: pointer of type atomic_t
+ * @a: the amount to add to v...
+ * @u: ...unless v is equal to u.
+ *
+ * Atomically adds @a to @v, if @v was not already @u.
+ * Returns the original value of @v.
+ */
+#ifndef atomic_fetch_add_unless
+static inline int atomic_fetch_add_unless(atomic_t *v, int a, int u)
+{
+	int c = atomic_read(v);
+
+	do {
+		if (unlikely(c == u))
+			break;
+	} while (!atomic_try_cmpxchg(v, &c, c + a));
+
+	return c;
+}
+#endif
+
 /**
 * atomic_add_unless - add unless the number is already a given value
 * @v: pointer of type atomic_t
 * @a: the amount to add to v...
 * @u: ...unless v is equal to u.
 *
- * Atomically adds @a to @v, so long as @v was not already @u.
- * Returns non-zero if @v was not @u, and zero otherwise.
+ * Atomically adds @a to @v, if @v was not already @u.
+ * Returns true if the addition was done.
 */
-static inline int atomic_add_unless(atomic_t *v, int a, int u)
+static inline bool atomic_add_unless(atomic_t *v, int a, int u)
 {
-	return __atomic_add_unless(v, a, u) != u;
+	return atomic_fetch_add_unless(v, a, u) != u;
 }

 /**
 * atomic_inc_not_zero - increment unless the number is zero
 * @v: pointer of type atomic_t
 *
- * Atomically increments @v by 1, so long as @v is non-zero.
- * Returns non-zero if @v was non-zero, and zero otherwise.
+ * Atomically increments @v by 1, if @v is non-zero.
+ * Returns true if the increment was done.
 */
 #ifndef atomic_inc_not_zero
 #define atomic_inc_not_zero(v)		atomic_add_unless((v), 1, 0)
 #endif

-#ifndef atomic_andnot
-static inline void atomic_andnot(int i, atomic_t *v)
+/**
+ * atomic_inc_and_test - increment and test
+ * @v: pointer of type atomic_t
+ *
+ * Atomically increments @v by 1
+ * and returns true if the result is zero, or false for all
+ * other cases.
+ */
+#ifndef atomic_inc_and_test
+static inline bool atomic_inc_and_test(atomic_t *v)
 {
-	atomic_and(~i, v);
-}
-
-static inline int atomic_fetch_andnot(int i, atomic_t *v)
-{
-	return atomic_fetch_and(~i, v);
-}
-
-static inline int atomic_fetch_andnot_relaxed(int i, atomic_t *v)
-{
-	return atomic_fetch_and_relaxed(~i, v);
-}
-
-static inline int atomic_fetch_andnot_acquire(int i, atomic_t *v)
-{
-	return atomic_fetch_and_acquire(~i, v);
-}
-
-static inline int atomic_fetch_andnot_release(int i, atomic_t *v)
-{
-	return atomic_fetch_and_release(~i, v);
+	return atomic_inc_return(v) == 0;
 }
 #endif

 /**
- * atomic_inc_not_zero_hint - increment if not null
+ * atomic_dec_and_test - decrement and test
 * @v: pointer of type atomic_t
- * @hint: probable value of the atomic before the increment
 *
- * This version of atomic_inc_not_zero() gives a hint of probable
- * value of the atomic. This helps processor to not read the memory
- * before doing the atomic read/modify/write cycle, lowering
- * number of bus transactions on some arches.
- *
- * Returns: 0 if increment was not done, 1 otherwise.
+ * Atomically decrements @v by 1 and
+ * returns true if the result is 0, or false for all other
+ * cases.
 */
-#ifndef atomic_inc_not_zero_hint
-static inline int atomic_inc_not_zero_hint(atomic_t *v, int hint)
+#ifndef atomic_dec_and_test
+static inline bool atomic_dec_and_test(atomic_t *v)
 {
-	int val, c = hint;
+	return atomic_dec_return(v) == 0;
+}
+#endif

-	/* sanity test, should be removed by compiler if hint is a constant */
-	if (!hint)
-		return atomic_inc_not_zero(v);
+/**
+ * atomic_sub_and_test - subtract value from variable and test result
+ * @i: integer value to subtract
+ * @v: pointer of type atomic_t
+ *
+ * Atomically subtracts @i from @v and returns
+ * true if the result is zero, or false for all
+ * other cases.
+ */
+#ifndef atomic_sub_and_test
+static inline bool atomic_sub_and_test(int i, atomic_t *v)
+{
+	return atomic_sub_return(i, v) == 0;
+}
+#endif

-	do {
-		val = atomic_cmpxchg(v, c, c + 1);
-		if (val == c)
-			return 1;
-		c = val;
-	} while (c);
-
-	return 0;
+/**
+ * atomic_add_negative - add and test if negative
+ * @i: integer value to add
+ * @v: pointer of type atomic_t
+ *
+ * Atomically adds @i to @v and returns true
+ * if the result is negative, or false when
+ * result is greater than or equal to zero.
+ */
+#ifndef atomic_add_negative
+static inline bool atomic_add_negative(int i, atomic_t *v)
+{
+	return atomic_add_return(i, v) < 0;
 }
 #endif

 #ifndef atomic_inc_unless_negative
-static inline int atomic_inc_unless_negative(atomic_t *p)
+static inline bool atomic_inc_unless_negative(atomic_t *v)
 {
-	int v, v1;
-	for (v = 0; v >= 0; v = v1) {
-		v1 = atomic_cmpxchg(p, v, v + 1);
-		if (likely(v1 == v))
-			return 1;
-	}
-	return 0;
+	int c = atomic_read(v);
+
+	do {
+		if (unlikely(c < 0))
+			return false;
+	} while (!atomic_try_cmpxchg(v, &c, c + 1));
+
+	return true;
 }
 #endif

 #ifndef atomic_dec_unless_positive
-static inline int atomic_dec_unless_positive(atomic_t *p)
+static inline bool atomic_dec_unless_positive(atomic_t *v)
 {
-	int v, v1;
-	for (v = 0; v <= 0; v = v1) {
-		v1 = atomic_cmpxchg(p, v, v - 1);
-		if (likely(v1 == v))
-			return 1;
-	}
-	return 0;
+	int c = atomic_read(v);
+
+	do {
+		if (unlikely(c > 0))
+			return false;
+	} while (!atomic_try_cmpxchg(v, &c, c - 1));
+
+	return true;
 }
 #endif

@@ -639,17 +708,14 @@ static inline int atomic_dec_unless_positive(atomic_t *p)
 #ifndef atomic_dec_if_positive
 static inline int atomic_dec_if_positive(atomic_t *v)
 {
-	int c, old, dec;
-	c = atomic_read(v);
-	for (;;) {
+	int dec, c = atomic_read(v);
+
+	do {
 		dec = c - 1;
 		if (unlikely(dec < 0))
 			break;
-		old = atomic_cmpxchg((v), c, dec);
-		if (likely(old == c))
-			break;
-		c = old;
-	}
+	} while (!atomic_try_cmpxchg(v, &c, dec));
+
 	return dec;
 }
 #endif
@@ -693,11 +759,23 @@ static inline int atomic_dec_if_positive(atomic_t *v)
 #endif
 #endif /* atomic64_add_return_relaxed */

+#ifndef atomic64_inc
+#define atomic64_inc(v)			atomic64_add(1, (v))
+#endif
+
 /* atomic64_inc_return_relaxed */
 #ifndef atomic64_inc_return_relaxed
+
+#ifndef atomic64_inc_return
+#define atomic64_inc_return(v)		atomic64_add_return(1, (v))
+#define atomic64_inc_return_relaxed(v)	atomic64_add_return_relaxed(1, (v))
+#define atomic64_inc_return_acquire(v)	atomic64_add_return_acquire(1, (v))
+#define atomic64_inc_return_release(v)	atomic64_add_return_release(1, (v))
+#else /* atomic64_inc_return */
 #define  atomic64_inc_return_relaxed	atomic64_inc_return
 #define  atomic64_inc_return_acquire	atomic64_inc_return
 #define  atomic64_inc_return_release	atomic64_inc_return
+#endif /* atomic64_inc_return */

 #else /* atomic64_inc_return_relaxed */

@@ -742,11 +820,23 @@ static inline int atomic_dec_if_positive(atomic_t *v)
 #endif
 #endif /* atomic64_sub_return_relaxed */

+#ifndef atomic64_dec
+#define atomic64_dec(v)			atomic64_sub(1, (v))
+#endif
+
 /* atomic64_dec_return_relaxed */
 #ifndef atomic64_dec_return_relaxed
+
+#ifndef atomic64_dec_return
+#define atomic64_dec_return(v)		atomic64_sub_return(1, (v))
+#define atomic64_dec_return_relaxed(v)	atomic64_sub_return_relaxed(1, (v))
+#define atomic64_dec_return_acquire(v)	atomic64_sub_return_acquire(1, (v))
+#define atomic64_dec_return_release(v)	atomic64_sub_return_release(1, (v))
+#else /* atomic64_dec_return */
 #define  atomic64_dec_return_relaxed	atomic64_dec_return
 #define  atomic64_dec_return_acquire	atomic64_dec_return
 #define  atomic64_dec_return_release	atomic64_dec_return
+#endif /* atomic64_dec_return */

 #else /* atomic64_dec_return_relaxed */

@@ -927,12 +1017,22 @@ static inline int atomic_dec_if_positive(atomic_t *v)
 #endif
 #endif /* atomic64_fetch_and_relaxed */

-#ifdef atomic64_andnot
-/* atomic64_fetch_andnot_relaxed */
+#ifndef atomic64_andnot
+#define atomic64_andnot(i, v)		atomic64_and(~(long long)(i), (v))
+#endif
+
 #ifndef atomic64_fetch_andnot_relaxed
-#define atomic64_fetch_andnot_relaxed	atomic64_fetch_andnot
-#define atomic64_fetch_andnot_acquire	atomic64_fetch_andnot
-#define atomic64_fetch_andnot_release	atomic64_fetch_andnot
+
+#ifndef atomic64_fetch_andnot
+#define atomic64_fetch_andnot(i, v)		atomic64_fetch_and(~(long long)(i), (v))
+#define atomic64_fetch_andnot_relaxed(i, v)	atomic64_fetch_and_relaxed(~(long long)(i), (v))
+#define atomic64_fetch_andnot_acquire(i, v)	atomic64_fetch_and_acquire(~(long long)(i), (v))
+#define atomic64_fetch_andnot_release(i, v)	atomic64_fetch_and_release(~(long long)(i), (v))
+#else /* atomic64_fetch_andnot */
+#define atomic64_fetch_andnot_relaxed		atomic64_fetch_andnot
+#define atomic64_fetch_andnot_acquire		atomic64_fetch_andnot
+#define atomic64_fetch_andnot_release		atomic64_fetch_andnot
+#endif /* atomic64_fetch_andnot */

 #else /* atomic64_fetch_andnot_relaxed */

@@ -951,7 +1051,6 @@ static inline int atomic_dec_if_positive(atomic_t *v)
 	__atomic_op_fence(atomic64_fetch_andnot, __VA_ARGS__)
 #endif
 #endif /* atomic64_fetch_andnot_relaxed */
-#endif /* atomic64_andnot */

 /* atomic64_fetch_xor_relaxed */
 #ifndef atomic64_fetch_xor_relaxed
@@ -1049,30 +1148,164 @@ static inline int atomic_dec_if_positive(atomic_t *v)
 #define atomic64_try_cmpxchg_release	atomic64_try_cmpxchg
 #endif /* atomic64_try_cmpxchg */

-#ifndef atomic64_andnot
-static inline void atomic64_andnot(long long i, atomic64_t *v)
+/**
+ * atomic64_fetch_add_unless - add unless the number is already a given value
+ * @v: pointer of type atomic64_t
+ * @a: the amount to add to v...
+ * @u: ...unless v is equal to u.
+ *
+ * Atomically adds @a to @v, if @v was not already @u.
+ * Returns the original value of @v.
+ */
+#ifndef atomic64_fetch_add_unless
+static inline long long atomic64_fetch_add_unless(atomic64_t *v, long long a,
+						  long long u)
 {
-	atomic64_and(~i, v);
+	long long c = atomic64_read(v);
+
+	do {
+		if (unlikely(c == u))
+			break;
+	} while (!atomic64_try_cmpxchg(v, &c, c + a));
+
+	return c;
+}
+#endif
+
+/**
+ * atomic64_add_unless - add unless the number is already a given value
+ * @v: pointer of type atomic_t
+ * @a: the amount to add to v...
+ * @u: ...unless v is equal to u.
+ *
+ * Atomically adds @a to @v, if @v was not already @u.
+ * Returns true if the addition was done.
+ */
+static inline bool atomic64_add_unless(atomic64_t *v, long long a, long long u)
+{
+	return atomic64_fetch_add_unless(v, a, u) != u;
 }

-static inline long long atomic64_fetch_andnot(long long i, atomic64_t *v)
-{
-	return atomic64_fetch_and(~i, v);
-}
+/**
+ * atomic64_inc_not_zero - increment unless the number is zero
+ * @v: pointer of type atomic64_t
+ *
+ * Atomically increments @v by 1, if @v is non-zero.
+ * Returns true if the increment was done.
+ */
+#ifndef atomic64_inc_not_zero
+#define atomic64_inc_not_zero(v)	atomic64_add_unless((v), 1, 0)
+#endif

-static inline long long atomic64_fetch_andnot_relaxed(long long i, atomic64_t *v)
+/**
+ * atomic64_inc_and_test - increment and test
+ * @v: pointer of type atomic64_t
+ *
+ * Atomically increments @v by 1
+ * and returns true if the result is zero, or false for all
+ * other cases.
+ */
+#ifndef atomic64_inc_and_test
+static inline bool atomic64_inc_and_test(atomic64_t *v)
 {
-	return atomic64_fetch_and_relaxed(~i, v);
+	return atomic64_inc_return(v) == 0;
 }
+#endif

-static inline long long atomic64_fetch_andnot_acquire(long long i, atomic64_t *v)
+/**
+ * atomic64_dec_and_test - decrement and test
+ * @v: pointer of type atomic64_t
+ *
+ * Atomically decrements @v by 1 and
+ * returns true if the result is 0, or false for all other
+ * cases.
+ */
+#ifndef atomic64_dec_and_test
+static inline bool atomic64_dec_and_test(atomic64_t *v)
 {
-	return atomic64_fetch_and_acquire(~i, v);
+	return atomic64_dec_return(v) == 0;
 }
+#endif

-static inline long long atomic64_fetch_andnot_release(long long i, atomic64_t *v)
+/**
+ * atomic64_sub_and_test - subtract value from variable and test result
+ * @i: integer value to subtract
+ * @v: pointer of type atomic64_t
+ *
+ * Atomically subtracts @i from @v and returns
+ * true if the result is zero, or false for all
+ * other cases.
+ */
+#ifndef atomic64_sub_and_test
+static inline bool atomic64_sub_and_test(long long i, atomic64_t *v)
 {
-	return atomic64_fetch_and_release(~i, v);
+	return atomic64_sub_return(i, v) == 0;
+}
+#endif
+
+/**
+ * atomic64_add_negative - add and test if negative
+ * @i: integer value to add
+ * @v: pointer of type atomic64_t
+ *
+ * Atomically adds @i to @v and returns true
+ * if the result is negative, or false when
+ * result is greater than or equal to zero.
+ */
+#ifndef atomic64_add_negative
+static inline bool atomic64_add_negative(long long i, atomic64_t *v)
+{
+	return atomic64_add_return(i, v) < 0;
+}
+#endif
+
+#ifndef atomic64_inc_unless_negative
+static inline bool atomic64_inc_unless_negative(atomic64_t *v)
+{
+	long long c = atomic64_read(v);
+
+	do {
+		if (unlikely(c < 0))
+			return false;
+	} while (!atomic64_try_cmpxchg(v, &c, c + 1));
+
+	return true;
+}
+#endif
+
+#ifndef atomic64_dec_unless_positive
+static inline bool atomic64_dec_unless_positive(atomic64_t *v)
+{
+	long long c = atomic64_read(v);
+
+	do {
+		if (unlikely(c > 0))
+			return false;
+	} while (!atomic64_try_cmpxchg(v, &c, c - 1));
+
+	return true;
+}
+#endif
+
+/*
+ * atomic64_dec_if_positive - decrement by 1 if old value positive
+ * @v: pointer of type atomic64_t
+ *
+ * The function returns the old value of *v minus 1, even if
+ * the atomic64 variable, v, was not decremented.
+ */
+#ifndef atomic64_dec_if_positive
+static inline long long atomic64_dec_if_positive(atomic64_t *v)
+{
+	long long dec, c = atomic64_read(v);
+
+	do {
+		dec = c - 1;
+		if (unlikely(dec < 0))
+			break;
+	} while (!atomic64_try_cmpxchg(v, &c, dec));
+
+	return dec;
 }
 #endif

--- a/include/linux/bitops.h
+++ b/include/linux/bitops.h
@@ -2,29 +2,9 @@
 #ifndef _LINUX_BITOPS_H
 #define _LINUX_BITOPS_H
 #include <asm/types.h>
+#include <linux/bits.h>

-#ifdef	__KERNEL__
-#define BIT(nr)			(1UL << (nr))
-#define BIT_ULL(nr)		(1ULL << (nr))
-#define BIT_MASK(nr)		(1UL << ((nr) % BITS_PER_LONG))
-#define BIT_WORD(nr)		((nr) / BITS_PER_LONG)
-#define BIT_ULL_MASK(nr)	(1ULL << ((nr) % BITS_PER_LONG_LONG))
-#define BIT_ULL_WORD(nr)	((nr) / BITS_PER_LONG_LONG)
-#define BITS_PER_BYTE		8
 #define BITS_TO_LONGS(nr)	DIV_ROUND_UP(nr, BITS_PER_BYTE * sizeof(long))
-#endif
-
-/*
- * Create a contiguous bitmask starting at bit position @l and ending at
- * position @h. For example
- * GENMASK_ULL(39, 21) gives us the 64bit vector 0x000000ffffe00000.
- */
-#define GENMASK(h, l) \
-	(((~0UL) - (1UL << (l)) + 1) & (~0UL >> (BITS_PER_LONG - 1 - (h))))
-
-#define GENMASK_ULL(h, l) \
-	(((~0ULL) - (1ULL << (l)) + 1) & \
-	 (~0ULL >> (BITS_PER_LONG_LONG - 1 - (h))))

 extern unsigned int __sw_hweight8(unsigned int w);
 extern unsigned int __sw_hweight16(unsigned int w);
--- a/include/linux/bits.h
+++ b/include/linux/bits.h
@@ -0,0 +1,26 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __LINUX_BITS_H
+#define __LINUX_BITS_H
+#include <asm/bitsperlong.h>
+
+#define BIT(nr)			(1UL << (nr))
+#define BIT_ULL(nr)		(1ULL << (nr))
+#define BIT_MASK(nr)		(1UL << ((nr) % BITS_PER_LONG))
+#define BIT_WORD(nr)		((nr) / BITS_PER_LONG)
+#define BIT_ULL_MASK(nr)	(1ULL << ((nr) % BITS_PER_LONG_LONG))
+#define BIT_ULL_WORD(nr)	((nr) / BITS_PER_LONG_LONG)
+#define BITS_PER_BYTE		8
+
+/*
+ * Create a contiguous bitmask starting at bit position @l and ending at
+ * position @h. For example
+ * GENMASK_ULL(39, 21) gives us the 64bit vector 0x000000ffffe00000.
+ */
+#define GENMASK(h, l) \
+	(((~0UL) - (1UL << (l)) + 1) & (~0UL >> (BITS_PER_LONG - 1 - (h))))
+
+#define GENMASK_ULL(h, l) \
+	(((~0ULL) - (1ULL << (l)) + 1) & \
+	 (~0ULL >> (BITS_PER_LONG_LONG - 1 - (h))))
+
+#endif	/* __LINUX_BITS_H */
--- a/include/linux/refcount.h
+++ b/include/linux/refcount.h
@@ -3,9 +3,10 @@
 #define _LINUX_REFCOUNT_H

 #include <linux/atomic.h>
-#include <linux/mutex.h>
-#include <linux/spinlock.h>
-#include <linux/kernel.h>
+#include <linux/compiler.h>
+#include <linux/spinlock_types.h>
+
+struct mutex;

 /**
 * struct refcount_t - variant of atomic_t specialized for reference counts
@@ -42,17 +43,30 @@ static inline unsigned int refcount_read(const refcount_t *r)
 	return atomic_read(&r->refs);
 }

+extern __must_check bool refcount_add_not_zero_checked(unsigned int i, refcount_t *r);
+extern void refcount_add_checked(unsigned int i, refcount_t *r);
+
+extern __must_check bool refcount_inc_not_zero_checked(refcount_t *r);
+extern void refcount_inc_checked(refcount_t *r);
+
+extern __must_check bool refcount_sub_and_test_checked(unsigned int i, refcount_t *r);
+
+extern __must_check bool refcount_dec_and_test_checked(refcount_t *r);
+extern void refcount_dec_checked(refcount_t *r);
+
 #ifdef CONFIG_REFCOUNT_FULL
-extern __must_check bool refcount_add_not_zero(unsigned int i, refcount_t *r);
-extern void refcount_add(unsigned int i, refcount_t *r);

-extern __must_check bool refcount_inc_not_zero(refcount_t *r);
-extern void refcount_inc(refcount_t *r);
+#define refcount_add_not_zero	refcount_add_not_zero_checked
+#define refcount_add		refcount_add_checked

-extern __must_check bool refcount_sub_and_test(unsigned int i, refcount_t *r);
+#define refcount_inc_not_zero	refcount_inc_not_zero_checked
+#define refcount_inc		refcount_inc_checked
+
+#define refcount_sub_and_test	refcount_sub_and_test_checked
+
+#define refcount_dec_and_test	refcount_dec_and_test_checked
+#define refcount_dec		refcount_dec_checked

-extern __must_check bool refcount_dec_and_test(refcount_t *r);
-extern void refcount_dec(refcount_t *r);
 #else
 # ifdef CONFIG_ARCH_HAS_REFCOUNT
 #  include <asm/refcount.h>
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -167,8 +167,8 @@ struct task_group;
 *   need_sleep = false;
 *   wake_up_state(p, TASK_UNINTERRUPTIBLE);
 *
- * Where wake_up_state() (and all other wakeup primitives) imply enough
- * barriers to order the store of the variable against wakeup.
+ * where wake_up_state() executes a full memory barrier before accessing the
+ * task state.
 *
 * Wakeup will do: if (@state & p->state) p->state = TASK_RUNNING, that is,
 * once it observes the TASK_UNINTERRUPTIBLE store the waking CPU can issue a
--- a/include/linux/spinlock.h
+++ b/include/linux/spinlock.h
@@ -114,29 +114,48 @@ do {								\
 #endif /*arch_spin_is_contended*/

 /*
- * This barrier must provide two things:
+ * smp_mb__after_spinlock() provides the equivalent of a full memory barrier
+ * between program-order earlier lock acquisitions and program-order later
+ * memory accesses.
 *
- *   - it must guarantee a STORE before the spin_lock() is ordered against a
- *     LOAD after it, see the comments at its two usage sites.
+ * This guarantees that the following two properties hold:
 *
- *   - it must ensure the critical section is RCsc.
+ *   1) Given the snippet:
 *
- * The latter is important for cases where we observe values written by other
- * CPUs in spin-loops, without barriers, while being subject to scheduling.
+ *	  { X = 0;  Y = 0; }
 *
- * CPU0			CPU1			CPU2
+ *	  CPU0				CPU1
 *
- *			for (;;) {
- *			  if (READ_ONCE(X))
- *			    break;
- *			}
- * X=1
- *			<sched-out>
- *						<sched-in>
- *						r = X;
+ *	  WRITE_ONCE(X, 1);		WRITE_ONCE(Y, 1);
+ *	  spin_lock(S);			smp_mb();
+ *	  smp_mb__after_spinlock();	r1 = READ_ONCE(X);
+ *	  r0 = READ_ONCE(Y);
+ *	  spin_unlock(S);
 *
- * without transitivity it could be that CPU1 observes X!=0 breaks the loop,
- * we get migrated and CPU2 sees X==0.
+ *      it is forbidden that CPU0 does not observe CPU1's store to Y (r0 = 0)
+ *      and CPU1 does not observe CPU0's store to X (r1 = 0); see the comments
+ *      preceding the call to smp_mb__after_spinlock() in __schedule() and in
+ *      try_to_wake_up().
+ *
+ *   2) Given the snippet:
+ *
+ *  { X = 0;  Y = 0; }
+ *
+ *  CPU0		CPU1				CPU2
+ *
+ *  spin_lock(S);	spin_lock(S);			r1 = READ_ONCE(Y);
+ *  WRITE_ONCE(X, 1);	smp_mb__after_spinlock();	smp_rmb();
+ *  spin_unlock(S);	r0 = READ_ONCE(X);		r2 = READ_ONCE(X);
+ *			WRITE_ONCE(Y, 1);
+ *			spin_unlock(S);
+ *
+ *      it is forbidden that CPU0's critical section executes before CPU1's
+ *      critical section (r0 = 1), CPU2 observes CPU1's store to Y (r1 = 1)
+ *      and CPU2 does not observe CPU0's store to X (r2 = 0); see the comments
+ *      preceding the calls to smp_rmb() in try_to_wake_up() for similar
+ *      snippets but "projected" onto two CPUs.
+ *
+ * Property (2) upgrades the lock to an RCsc lock.
 *
 * Since most load-store architectures implement ACQUIRE with an smp_mb() after
 * the LL/SC loop, they need no further barriers. Similarly all our TSO