Merge tag 'locking-core-2020-12-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull locking updates from Thomas Gleixner:
 "A moderate set of locking updates:

   - A few extensions to the rwsem API and support for opportunistic
     spinning and lock stealing

   - lockdep selftest improvements

   - Documentation updates

   - Cleanups and small fixes all over the place"

* tag 'locking-core-2020-12-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (21 commits)
  seqlock: kernel-doc: Specify when preemption is automatically altered
  seqlock: Prefix internal seqcount_t-only macros with a "do_"
  Documentation: seqlock: s/LOCKTYPE/LOCKNAME/g
  locking/rwsem: Remove reader optimistic spinning
  locking/rwsem: Enable reader optimistic lock stealing
  locking/rwsem: Prevent potential lock starvation
  locking/rwsem: Pass the current atomic count to rwsem_down_read_slowpath()
  locking/rwsem: Fold __down_{read,write}*()
  locking/rwsem: Introduce rwsem_write_trylock()
  locking/rwsem: Better collate rwsem_read_trylock()
  rwsem: Implement down_read_interruptible
  rwsem: Implement down_read_killable_nested
  refcount: Fix a kernel-doc markup
  completion: Drop init_completion define
  atomic: Update MAINTAINERS
  atomic: Delete obsolete documentation
  seqlock: Rename __seqprop() users
  lockdep/selftest: Add spin_nest_lock test
  lockdep/selftests: Fix PROVE_RAW_LOCK_NESTING
  seqlock: avoid -Wshadow warnings
  ...

4 files changed, 69 insertions, 62 deletions

diff --git a/include/linux/completion.h b/include/linux/completion.h
index bf8e77001f18..51d9ab079629 100644
--- a/include/linux/completion.h
+++ b/include/linux/completion.h
@@ -28,8 +28,7 @@ struct completion {
 	struct swait_queue_head wait;
 };
 
-#define init_completion_map(x, m) __init_completion(x)
-#define init_completion(x) __init_completion(x)
+#define init_completion_map(x, m) init_completion(x)
 static inline void complete_acquire(struct completion *x) {}
 static inline void complete_release(struct completion *x) {}
 
@@ -82,7 +81,7 @@ static inline void complete_release(struct completion *x) {}
  * This inline function will initialize a dynamically created completion
  * structure.
  */
-static inline void __init_completion(struct completion *x)
+static inline void init_completion(struct completion *x)
 {
 	x->done = 0;
 	init_swait_queue_head(&x->wait);
diff --git a/include/linux/refcount.h b/include/linux/refcount.h
index 497990c69b0b..b8a6e387f8f9 100644
--- a/include/linux/refcount.h
+++ b/include/linux/refcount.h
@@ -101,7 +101,7 @@
 struct mutex;
 
 /**
- * struct refcount_t - variant of atomic_t specialized for reference counts
+ * typedef refcount_t - variant of atomic_t specialized for reference counts
  * @refs: atomic_t counter field
  *
  * The counter saturates at REFCOUNT_SATURATED and will not move once
diff --git a/include/linux/rwsem.h b/include/linux/rwsem.h
index 25e3fde85617..4c715be48717 100644
--- a/include/linux/rwsem.h
+++ b/include/linux/rwsem.h
@@ -123,6 +123,7 @@ static inline int rwsem_is_contended(struct rw_semaphore *sem)
  * lock for reading
  */
 extern void down_read(struct rw_semaphore *sem);
+extern int __must_check down_read_interruptible(struct rw_semaphore *sem);
 extern int __must_check down_read_killable(struct rw_semaphore *sem);
 
 /*
@@ -171,6 +172,7 @@ extern void downgrade_write(struct rw_semaphore *sem);
  * See Documentation/locking/lockdep-design.rst for more details.)
  */
 extern void down_read_nested(struct rw_semaphore *sem, int subclass);
+extern int __must_check down_read_killable_nested(struct rw_semaphore *sem, int subclass);
 extern void down_write_nested(struct rw_semaphore *sem, int subclass);
 extern int down_write_killable_nested(struct rw_semaphore *sem, int subclass);
 extern void _down_write_nest_lock(struct rw_semaphore *sem, struct lockdep_map *nest_lock);
@@ -191,6 +193,7 @@ extern void down_read_non_owner(struct rw_semaphore *sem);
 extern void up_read_non_owner(struct rw_semaphore *sem);
 #else
 # define down_read_nested(sem, subclass)		down_read(sem)
+# define down_read_killable_nested(sem, subclass)	down_read_killable(sem)
 # define down_write_nest_lock(sem, nest_lock)	down_write(sem)
 # define down_write_nested(sem, subclass)	down_write(sem)
 # define down_write_killable_nested(sem, subclass)	down_write_killable(sem)
diff --git a/include/linux/seqlock.h b/include/linux/seqlock.h
index cbfc78b92b65..2f7bb92b4c9e 100644
--- a/include/linux/seqlock.h
+++ b/include/linux/seqlock.h
@@ -307,10 +307,10 @@ SEQCOUNT_LOCKNAME(ww_mutex,     struct ww_mutex, true,     &s->lock->base, ww_mu
 	__seqprop_case((s),	mutex,		prop),			\
 	__seqprop_case((s),	ww_mutex,	prop))
 
-#define __seqcount_ptr(s)		__seqprop(s, ptr)
-#define __seqcount_sequence(s)		__seqprop(s, sequence)
-#define __seqcount_lock_preemptible(s)	__seqprop(s, preemptible)
-#define __seqcount_assert_lock_held(s)	__seqprop(s, assert)
+#define seqprop_ptr(s)			__seqprop(s, ptr)
+#define seqprop_sequence(s)		__seqprop(s, sequence)
+#define seqprop_preemptible(s)		__seqprop(s, preemptible)
+#define seqprop_assert(s)		__seqprop(s, assert)
 
 /**
  * __read_seqcount_begin() - begin a seqcount_t read section w/o barrier
@@ -328,13 +328,13 @@ SEQCOUNT_LOCKNAME(ww_mutex,     struct ww_mutex, true,     &s->lock->base, ww_mu
  */
 #define __read_seqcount_begin(s)					\
 ({									\
-	unsigned seq;							\
+	unsigned __seq;							\
 									\
-	while ((seq = __seqcount_sequence(s)) & 1)			\
+	while ((__seq = seqprop_sequence(s)) & 1)			\
 		cpu_relax();						\
 									\
 	kcsan_atomic_next(KCSAN_SEQLOCK_REGION_MAX);			\
-	seq;								\
+	__seq;								\
 })
 
 /**
@@ -345,10 +345,10 @@ SEQCOUNT_LOCKNAME(ww_mutex,     struct ww_mutex, true,     &s->lock->base, ww_mu
  */
 #define raw_read_seqcount_begin(s)					\
 ({									\
-	unsigned seq = __read_seqcount_begin(s);			\
+	unsigned _seq = __read_seqcount_begin(s);			\
 									\
 	smp_rmb();							\
-	seq;								\
+	_seq;								\
 })
 
 /**
@@ -359,7 +359,7 @@ SEQCOUNT_LOCKNAME(ww_mutex,     struct ww_mutex, true,     &s->lock->base, ww_mu
  */
 #define read_seqcount_begin(s)						\
 ({									\
-	seqcount_lockdep_reader_access(__seqcount_ptr(s));		\
+	seqcount_lockdep_reader_access(seqprop_ptr(s));			\
 	raw_read_seqcount_begin(s);					\
 })
 
@@ -376,11 +376,11 @@ SEQCOUNT_LOCKNAME(ww_mutex,     struct ww_mutex, true,     &s->lock->base, ww_mu
  */
 #define raw_read_seqcount(s)						\
 ({									\
-	unsigned seq = __seqcount_sequence(s);				\
+	unsigned __seq = seqprop_sequence(s);				\
 									\
 	smp_rmb();							\
 	kcsan_atomic_next(KCSAN_SEQLOCK_REGION_MAX);			\
-	seq;								\
+	__seq;								\
 })
 
 /**
@@ -425,9 +425,9 @@ SEQCOUNT_LOCKNAME(ww_mutex,     struct ww_mutex, true,     &s->lock->base, ww_mu
  * Return: true if a read section retry is required, else false
  */
 #define __read_seqcount_retry(s, start)					\
-	__read_seqcount_t_retry(__seqcount_ptr(s), start)
+	do___read_seqcount_retry(seqprop_ptr(s), start)
 
-static inline int __read_seqcount_t_retry(const seqcount_t *s, unsigned start)
+static inline int do___read_seqcount_retry(const seqcount_t *s, unsigned start)
 {
 	kcsan_atomic_next(0);
 	return unlikely(READ_ONCE(s->sequence) != start);
@@ -445,27 +445,29 @@ static inline int __read_seqcount_t_retry(const seqcount_t *s, unsigned start)
  * Return: true if a read section retry is required, else false
  */
 #define read_seqcount_retry(s, start)					\
-	read_seqcount_t_retry(__seqcount_ptr(s), start)
+	do_read_seqcount_retry(seqprop_ptr(s), start)
 
-static inline int read_seqcount_t_retry(const seqcount_t *s, unsigned start)
+static inline int do_read_seqcount_retry(const seqcount_t *s, unsigned start)
 {
 	smp_rmb();
-	return __read_seqcount_t_retry(s, start);
+	return do___read_seqcount_retry(s, start);
 }
 
 /**
  * raw_write_seqcount_begin() - start a seqcount_t write section w/o lockdep
  * @s: Pointer to seqcount_t or any of the seqcount_LOCKNAME_t variants
+ *
+ * Context: check write_seqcount_begin()
  */
 #define raw_write_seqcount_begin(s)					\
 do {									\
-	if (__seqcount_lock_preemptible(s))				\
+	if (seqprop_preemptible(s))					\
 		preempt_disable();					\
 									\
-	raw_write_seqcount_t_begin(__seqcount_ptr(s));			\
+	do_raw_write_seqcount_begin(seqprop_ptr(s));			\
 } while (0)
 
-static inline void raw_write_seqcount_t_begin(seqcount_t *s)
+static inline void do_raw_write_seqcount_begin(seqcount_t *s)
 {
 	kcsan_nestable_atomic_begin();
 	s->sequence++;
@@ -475,16 +477,18 @@ static inline void raw_write_seqcount_t_begin(seqcount_t *s)
 /**
  * raw_write_seqcount_end() - end a seqcount_t write section w/o lockdep
  * @s: Pointer to seqcount_t or any of the seqcount_LOCKNAME_t variants
+ *
+ * Context: check write_seqcount_end()
  */
 #define raw_write_seqcount_end(s)					\
 do {									\
-	raw_write_seqcount_t_end(__seqcount_ptr(s));			\
+	do_raw_write_seqcount_end(seqprop_ptr(s));			\
 									\
-	if (__seqcount_lock_preemptible(s))				\
+	if (seqprop_preemptible(s))					\
 		preempt_enable();					\
 } while (0)
 
-static inline void raw_write_seqcount_t_end(seqcount_t *s)
+static inline void do_raw_write_seqcount_end(seqcount_t *s)
 {
 	smp_wmb();
 	s->sequence++;
@@ -498,20 +502,21 @@ static inline void raw_write_seqcount_t_end(seqcount_t *s)
  * @subclass: lockdep nesting level
  *
  * See Documentation/locking/lockdep-design.rst
+ * Context: check write_seqcount_begin()
  */
 #define write_seqcount_begin_nested(s, subclass)			\
 do {									\
-	__seqcount_assert_lock_held(s);					\
+	seqprop_assert(s);						\
 									\
-	if (__seqcount_lock_preemptible(s))				\
+	if (seqprop_preemptible(s))					\
 		preempt_disable();					\
 									\
-	write_seqcount_t_begin_nested(__seqcount_ptr(s), subclass);	\
+	do_write_seqcount_begin_nested(seqprop_ptr(s), subclass);	\
 } while (0)
 
-static inline void write_seqcount_t_begin_nested(seqcount_t *s, int subclass)
+static inline void do_write_seqcount_begin_nested(seqcount_t *s, int subclass)
 {
-	raw_write_seqcount_t_begin(s);
+	do_raw_write_seqcount_begin(s);
 	seqcount_acquire(&s->dep_map, subclass, 0, _RET_IP_);
 }
 
@@ -519,46 +524,46 @@ static inline void write_seqcount_t_begin_nested(seqcount_t *s, int subclass)
  * write_seqcount_begin() - start a seqcount_t write side critical section
  * @s: Pointer to seqcount_t or any of the seqcount_LOCKNAME_t variants
  *
- * write_seqcount_begin opens a write side critical section of the given
- * seqcount_t.
- *
- * Context: seqcount_t write side critical sections must be serialized and
- * non-preemptible. If readers can be invoked from hardirq or softirq
+ * Context: sequence counter write side sections must be serialized and
+ * non-preemptible. Preemption will be automatically disabled if and
+ * only if the seqcount write serialization lock is associated, and
+ * preemptible.  If readers can be invoked from hardirq or softirq
  * context, interrupts or bottom halves must be respectively disabled.
  */
 #define write_seqcount_begin(s)						\
 do {									\
-	__seqcount_assert_lock_held(s);					\
+	seqprop_assert(s);						\
 									\
-	if (__seqcount_lock_preemptible(s))				\
+	if (seqprop_preemptible(s))					\
 		preempt_disable();					\
 									\
-	write_seqcount_t_begin(__seqcount_ptr(s));			\
+	do_write_seqcount_begin(seqprop_ptr(s));			\
 } while (0)
 
-static inline void write_seqcount_t_begin(seqcount_t *s)
+static inline void do_write_seqcount_begin(seqcount_t *s)
 {
-	write_seqcount_t_begin_nested(s, 0);
+	do_write_seqcount_begin_nested(s, 0);
 }
 
 /**
  * write_seqcount_end() - end a seqcount_t write side critical section
  * @s: Pointer to seqcount_t or any of the seqcount_LOCKNAME_t variants
  *
- * The write section must've been opened with write_seqcount_begin().
+ * Context: Preemption will be automatically re-enabled if and only if
+ * the seqcount write serialization lock is associated, and preemptible.
  */
 #define write_seqcount_end(s)						\
 do {									\
-	write_seqcount_t_end(__seqcount_ptr(s));			\
+	do_write_seqcount_end(seqprop_ptr(s));				\
 									\
-	if (__seqcount_lock_preemptible(s))				\
+	if (seqprop_preemptible(s))					\
 		preempt_enable();					\
 } while (0)
 
-static inline void write_seqcount_t_end(seqcount_t *s)
+static inline void do_write_seqcount_end(seqcount_t *s)
 {
 	seqcount_release(&s->dep_map, _RET_IP_);
-	raw_write_seqcount_t_end(s);
+	do_raw_write_seqcount_end(s);
 }
 
 /**
@@ -603,9 +608,9 @@ static inline void write_seqcount_t_end(seqcount_t *s)
  *      }
  */
 #define raw_write_seqcount_barrier(s)					\
-	raw_write_seqcount_t_barrier(__seqcount_ptr(s))
+	do_raw_write_seqcount_barrier(seqprop_ptr(s))
 
-static inline void raw_write_seqcount_t_barrier(seqcount_t *s)
+static inline void do_raw_write_seqcount_barrier(seqcount_t *s)
 {
 	kcsan_nestable_atomic_begin();
 	s->sequence++;
@@ -623,9 +628,9 @@ static inline void raw_write_seqcount_t_barrier(seqcount_t *s)
  * will complete successfully and see data older than this.
  */
 #define write_seqcount_invalidate(s)					\
-	write_seqcount_t_invalidate(__seqcount_ptr(s))
+	do_write_seqcount_invalidate(seqprop_ptr(s))
 
-static inline void write_seqcount_t_invalidate(seqcount_t *s)
+static inline void do_write_seqcount_invalidate(seqcount_t *s)
 {
 	smp_wmb();
 	kcsan_nestable_atomic_begin();
@@ -865,9 +870,9 @@ static inline unsigned read_seqretry(const seqlock_t *sl, unsigned start)
 }
 
 /*
- * For all seqlock_t write side functions, use write_seqcount_*t*_begin()
- * instead of the generic write_seqcount_begin(). This way, no redundant
- * lockdep_assert_held() checks are added.
+ * For all seqlock_t write side functions, use the the internal
+ * do_write_seqcount_begin() instead of generic write_seqcount_begin().
+ * This way, no redundant lockdep_assert_held() checks are added.
  */
 
 /**
@@ -886,7 +891,7 @@ static inline unsigned read_seqretry(const seqlock_t *sl, unsigned start)
 static inline void write_seqlock(seqlock_t *sl)
 {
 	spin_lock(&sl->lock);
-	write_seqcount_t_begin(&sl->seqcount.seqcount);
+	do_write_seqcount_begin(&sl->seqcount.seqcount);
 }
 
 /**
@@ -898,7 +903,7 @@ static inline void write_seqlock(seqlock_t *sl)
  */
 static inline void write_sequnlock(seqlock_t *sl)
 {
-	write_seqcount_t_end(&sl->seqcount.seqcount);
+	do_write_seqcount_end(&sl->seqcount.seqcount);
 	spin_unlock(&sl->lock);
 }
 
@@ -912,7 +917,7 @@ static inline void write_sequnlock(seqlock_t *sl)
 static inline void write_seqlock_bh(seqlock_t *sl)
 {
 	spin_lock_bh(&sl->lock);
-	write_seqcount_t_begin(&sl->seqcount.seqcount);
+	do_write_seqcount_begin(&sl->seqcount.seqcount);
 }
 
 /**
@@ -925,7 +930,7 @@ static inline void write_seqlock_bh(seqlock_t *sl)
  */
 static inline void write_sequnlock_bh(seqlock_t *sl)
 {
-	write_seqcount_t_end(&sl->seqcount.seqcount);
+	do_write_seqcount_end(&sl->seqcount.seqcount);
 	spin_unlock_bh(&sl->lock);
 }
 
@@ -939,7 +944,7 @@ static inline void write_sequnlock_bh(seqlock_t *sl)
 static inline void write_seqlock_irq(seqlock_t *sl)
 {
 	spin_lock_irq(&sl->lock);
-	write_seqcount_t_begin(&sl->seqcount.seqcount);
+	do_write_seqcount_begin(&sl->seqcount.seqcount);
 }
 
 /**
@@ -951,7 +956,7 @@ static inline void write_seqlock_irq(seqlock_t *sl)
  */
 static inline void write_sequnlock_irq(seqlock_t *sl)
 {
-	write_seqcount_t_end(&sl->seqcount.seqcount);
+	do_write_seqcount_end(&sl->seqcount.seqcount);
 	spin_unlock_irq(&sl->lock);
 }
 
@@ -960,7 +965,7 @@ static inline unsigned long __write_seqlock_irqsave(seqlock_t *sl)
 	unsigned long flags;
 
 	spin_lock_irqsave(&sl->lock, flags);
-	write_seqcount_t_begin(&sl->seqcount.seqcount);
+	do_write_seqcount_begin(&sl->seqcount.seqcount);
 	return flags;
 }
 
@@ -989,7 +994,7 @@ static inline unsigned long __write_seqlock_irqsave(seqlock_t *sl)
 static inline void
 write_sequnlock_irqrestore(seqlock_t *sl, unsigned long flags)
 {
-	write_seqcount_t_end(&sl->seqcount.seqcount);
+	do_write_seqcount_end(&sl->seqcount.seqcount);
 	spin_unlock_irqrestore(&sl->lock, flags);
 }