1 files changed, 74 insertions, 114 deletions

diff --git a/drivers/tty/tty_ldsem.c b/drivers/tty/tty_ldsem.c
index 22fad8ad5ac2..4e18031a5ca3 100644
--- a/drivers/tty/tty_ldsem.c
+++ b/drivers/tty/tty_ldsem.c
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0
 /*
  * Ldisc rw semaphore
  *
@@ -22,9 +23,6 @@
  * Michel Lespinasse <walken@google.com>.
  *
  * Copyright (C) 2013 Peter Hurley <peter@hurleysoftware.com>
- *
- * This file may be redistributed under the terms of the GNU General Public
- * License v2.
  */
 
 #include <linux/list.h>
@@ -32,36 +30,8 @@
 #include <linux/atomic.h>
 #include <linux/tty.h>
 #include <linux/sched.h>
-
-
-#ifdef CONFIG_DEBUG_LOCK_ALLOC
-# define __acq(l, s, t, r, c, n, i)		\
-				lock_acquire(&(l)->dep_map, s, t, r, c, n, i)
-# define __rel(l, n, i)				\
-				lock_release(&(l)->dep_map, n, i)
-# ifdef CONFIG_PROVE_LOCKING
-#  define lockdep_acquire(l, s, t, i)		__acq(l, s, t, 0, 2, NULL, i)
-#  define lockdep_acquire_nest(l, s, t, n, i)	__acq(l, s, t, 0, 2, n, i)
-#  define lockdep_acquire_read(l, s, t, i)	__acq(l, s, t, 1, 2, NULL, i)
-#  define lockdep_release(l, n, i)		__rel(l, n, i)
-# else
-#  define lockdep_acquire(l, s, t, i)		__acq(l, s, t, 0, 1, NULL, i)
-#  define lockdep_acquire_nest(l, s, t, n, i)	__acq(l, s, t, 0, 1, n, i)
-#  define lockdep_acquire_read(l, s, t, i)	__acq(l, s, t, 1, 1, NULL, i)
-#  define lockdep_release(l, n, i)		__rel(l, n, i)
-# endif
-#else
-# define lockdep_acquire(l, s, t, i)		do { } while (0)
-# define lockdep_acquire_nest(l, s, t, n, i)	do { } while (0)
-# define lockdep_acquire_read(l, s, t, i)	do { } while (0)
-# define lockdep_release(l, n, i)		do { } while (0)
-#endif
-
-#ifdef CONFIG_LOCK_STAT
-# define lock_stat(_lock, stat)		lock_##stat(&(_lock)->dep_map, _RET_IP_)
-#else
-# define lock_stat(_lock, stat)		do { } while (0)
-#endif
+#include <linux/sched/debug.h>
+#include <linux/sched/task.h>
 
 
 #if BITS_PER_LONG == 64
@@ -81,18 +51,6 @@ struct ldsem_waiter {
 	struct task_struct *task;
 };
 
-static inline long ldsem_atomic_update(long delta, struct ld_semaphore *sem)
-{
-	return atomic_long_add_return(delta, (atomic_long_t *)&sem->count);
-}
-
-static inline int ldsem_cmpxchg(long *old, long new, struct ld_semaphore *sem)
-{
-	long tmp = *old;
-	*old = atomic_long_cmpxchg(&sem->count, *old, new);
-	return *old == tmp;
-}
-
 /*
  * Initialize an ldsem:
  */
@@ -106,7 +64,7 @@ void __init_ldsem(struct ld_semaphore *sem, const char *name,
 	debug_check_no_locks_freed((void *)sem, sizeof(*sem));
 	lockdep_init_map(&sem->dep_map, name, key, 0);
 #endif
-	sem->count = LDSEM_UNLOCKED;
+	atomic_long_set(&sem->count, LDSEM_UNLOCKED);
 	sem->wait_readers = 0;
 	raw_spin_lock_init(&sem->wait_lock);
 	INIT_LIST_HEAD(&sem->read_wait);
@@ -119,23 +77,23 @@ static void __ldsem_wake_readers(struct ld_semaphore *sem)
 	struct task_struct *tsk;
 	long adjust, count;
 
-	/* Try to grant read locks to all readers on the read wait list.
+	/*
+	 * Try to grant read locks to all readers on the read wait list.
 	 * Note the 'active part' of the count is incremented by
 	 * the number of readers before waking any processes up.
 	 */
 	adjust = sem->wait_readers * (LDSEM_ACTIVE_BIAS - LDSEM_WAIT_BIAS);
-	count = ldsem_atomic_update(adjust, sem);
+	count = atomic_long_add_return(adjust, &sem->count);
 	do {
 		if (count > 0)
 			break;
-		if (ldsem_cmpxchg(&count, count - adjust, sem))
+		if (atomic_long_try_cmpxchg(&sem->count, &count, count - adjust))
 			return;
 	} while (1);
 
 	list_for_each_entry_safe(waiter, next, &sem->read_wait, list) {
 		tsk = waiter->task;
-		smp_mb();
-		waiter->task = NULL;
+		smp_store_release(&waiter->task, NULL);
 		wake_up_process(tsk);
 		put_task_struct(tsk);
 	}
@@ -145,14 +103,15 @@ static void __ldsem_wake_readers(struct ld_semaphore *sem)
 
 static inline int writer_trylock(struct ld_semaphore *sem)
 {
-	/* only wake this writer if the active part of the count can be
+	/*
+	 * Only wake this writer if the active part of the count can be
 	 * transitioned from 0 -> 1
 	 */
-	long count = ldsem_atomic_update(LDSEM_ACTIVE_BIAS, sem);
+	long count = atomic_long_add_return(LDSEM_ACTIVE_BIAS, &sem->count);
 	do {
 		if ((count & LDSEM_ACTIVE_MASK) == LDSEM_ACTIVE_BIAS)
 			return 1;
-		if (ldsem_cmpxchg(&count, count - LDSEM_ACTIVE_BIAS, sem))
+		if (atomic_long_try_cmpxchg(&sem->count, &count, count - LDSEM_ACTIVE_BIAS))
 			return 0;
 	} while (1);
 }
@@ -197,18 +156,21 @@ static struct ld_semaphore __sched *
 down_read_failed(struct ld_semaphore *sem, long count, long timeout)
 {
 	struct ldsem_waiter waiter;
-	struct task_struct *tsk = current;
 	long adjust = -LDSEM_ACTIVE_BIAS + LDSEM_WAIT_BIAS;
 
 	/* set up my own style of waitqueue */
 	raw_spin_lock_irq(&sem->wait_lock);
 
-	/* Try to reverse the lock attempt but if the count has changed
-	 * so that reversing fails, check if there are are no waiters,
-	 * and early-out if not */
+	/*
+	 * Try to reverse the lock attempt but if the count has changed
+	 * so that reversing fails, check if there are no waiters,
+	 * and early-out if not
+	 */
 	do {
-		if (ldsem_cmpxchg(&count, count + adjust, sem))
+		if (atomic_long_try_cmpxchg(&sem->count, &count, count + adjust)) {
+			count += adjust;
 			break;
+		}
 		if (count > 0) {
 			raw_spin_unlock_irq(&sem->wait_lock);
 			return sem;
@@ -218,8 +180,8 @@ down_read_failed(struct ld_semaphore *sem, long count, long timeout)
 	list_add_tail(&waiter.list, &sem->read_wait);
 	sem->wait_readers++;
 
-	waiter.task = tsk;
-	get_task_struct(tsk);
+	waiter.task = current;
+	get_task_struct(current);
 
 	/* if there are no active locks, wake the new lock owner(s) */
 	if ((count & LDSEM_ACTIVE_MASK) == 0)
@@ -229,24 +191,27 @@ down_read_failed(struct ld_semaphore *sem, long count, long timeout)
 
 	/* wait to be given the lock */
 	for (;;) {
-		set_task_state(tsk, TASK_UNINTERRUPTIBLE);
+		set_current_state(TASK_UNINTERRUPTIBLE);
 
-		if (!waiter.task)
+		if (!smp_load_acquire(&waiter.task))
 			break;
 		if (!timeout)
 			break;
 		timeout = schedule_timeout(timeout);
 	}
 
-	__set_task_state(tsk, TASK_RUNNING);
+	__set_current_state(TASK_RUNNING);
 
 	if (!timeout) {
-		/* lock timed out but check if this task was just
+		/*
+		 * Lock timed out but check if this task was just
 		 * granted lock ownership - if so, pretend there
-		 * was no timeout; otherwise, cleanup lock wait */
+		 * was no timeout; otherwise, cleanup lock wait.
+		 */
 		raw_spin_lock_irq(&sem->wait_lock);
 		if (waiter.task) {
-			ldsem_atomic_update(-LDSEM_WAIT_BIAS, sem);
+			atomic_long_add_return(-LDSEM_WAIT_BIAS, &sem->count);
+			sem->wait_readers--;
 			list_del(&waiter.list);
 			raw_spin_unlock_irq(&sem->wait_lock);
 			put_task_struct(waiter.task);
@@ -265,18 +230,19 @@ static struct ld_semaphore __sched *
 down_write_failed(struct ld_semaphore *sem, long count, long timeout)
 {
 	struct ldsem_waiter waiter;
-	struct task_struct *tsk = current;
 	long adjust = -LDSEM_ACTIVE_BIAS;
 	int locked = 0;
 
 	/* set up my own style of waitqueue */
 	raw_spin_lock_irq(&sem->wait_lock);
 
-	/* Try to reverse the lock attempt but if the count has changed
+	/*
+	 * Try to reverse the lock attempt but if the count has changed
 	 * so that reversing fails, check if the lock is now owned,
-	 * and early-out if so */
+	 * and early-out if so.
+	 */
 	do {
-		if (ldsem_cmpxchg(&count, count + adjust, sem))
+		if (atomic_long_try_cmpxchg(&sem->count, &count, count + adjust))
 			break;
 		if ((count & LDSEM_ACTIVE_MASK) == LDSEM_ACTIVE_BIAS) {
 			raw_spin_unlock_irq(&sem->wait_lock);
@@ -286,26 +252,37 @@ down_write_failed(struct ld_semaphore *sem, long count, long timeout)
 
 	list_add_tail(&waiter.list, &sem->write_wait);
 
-	waiter.task = tsk;
+	waiter.task = current;
 
-	set_task_state(tsk, TASK_UNINTERRUPTIBLE);
+	set_current_state(TASK_UNINTERRUPTIBLE);
 	for (;;) {
 		if (!timeout)
 			break;
 		raw_spin_unlock_irq(&sem->wait_lock);
 		timeout = schedule_timeout(timeout);
 		raw_spin_lock_irq(&sem->wait_lock);
-		set_task_state(tsk, TASK_UNINTERRUPTIBLE);
-		if ((locked = writer_trylock(sem)))
+		set_current_state(TASK_UNINTERRUPTIBLE);
+		locked = writer_trylock(sem);
+		if (locked)
 			break;
 	}
 
 	if (!locked)
-		ldsem_atomic_update(-LDSEM_WAIT_BIAS, sem);
+		atomic_long_add_return(-LDSEM_WAIT_BIAS, &sem->count);
 	list_del(&waiter.list);
+
+	/*
+	 * In case of timeout, wake up every reader who gave the right of way
+	 * to writer. Prevent separation readers into two groups:
+	 * one that helds semaphore and another that sleeps.
+	 * (in case of no contention with a writer)
+	 */
+	if (!locked && list_empty(&sem->write_wait))
+		__ldsem_wake_readers(sem);
+
 	raw_spin_unlock_irq(&sem->wait_lock);
 
-	__set_task_state(tsk, TASK_RUNNING);
+	__set_current_state(TASK_RUNNING);
 
 	/* lock wait may have timed out */
 	if (!locked)
@@ -315,41 +292,41 @@ down_write_failed(struct ld_semaphore *sem, long count, long timeout)
 
 
 
-static inline int __ldsem_down_read_nested(struct ld_semaphore *sem,
+static int __ldsem_down_read_nested(struct ld_semaphore *sem,
 					   int subclass, long timeout)
 {
 	long count;
 
-	lockdep_acquire_read(sem, subclass, 0, _RET_IP_);
+	rwsem_acquire_read(&sem->dep_map, subclass, 0, _RET_IP_);
 
-	count = ldsem_atomic_update(LDSEM_READ_BIAS, sem);
+	count = atomic_long_add_return(LDSEM_READ_BIAS, &sem->count);
 	if (count <= 0) {
-		lock_stat(sem, contended);
+		lock_contended(&sem->dep_map, _RET_IP_);
 		if (!down_read_failed(sem, count, timeout)) {
-			lockdep_release(sem, 1, _RET_IP_);
+			rwsem_release(&sem->dep_map, _RET_IP_);
 			return 0;
 		}
 	}
-	lock_stat(sem, acquired);
+	lock_acquired(&sem->dep_map, _RET_IP_);
 	return 1;
 }
 
-static inline int __ldsem_down_write_nested(struct ld_semaphore *sem,
+static int __ldsem_down_write_nested(struct ld_semaphore *sem,
 					    int subclass, long timeout)
 {
 	long count;
 
-	lockdep_acquire(sem, subclass, 0, _RET_IP_);
+	rwsem_acquire(&sem->dep_map, subclass, 0, _RET_IP_);
 
-	count = ldsem_atomic_update(LDSEM_WRITE_BIAS, sem);
+	count = atomic_long_add_return(LDSEM_WRITE_BIAS, &sem->count);
 	if ((count & LDSEM_ACTIVE_MASK) != LDSEM_ACTIVE_BIAS) {
-		lock_stat(sem, contended);
+		lock_contended(&sem->dep_map, _RET_IP_);
 		if (!down_write_failed(sem, count, timeout)) {
-			lockdep_release(sem, 1, _RET_IP_);
+			rwsem_release(&sem->dep_map, _RET_IP_);
 			return 0;
 		}
 	}
-	lock_stat(sem, acquired);
+	lock_acquired(&sem->dep_map, _RET_IP_);
 	return 1;
 }
 
@@ -368,12 +345,12 @@ int __sched ldsem_down_read(struct ld_semaphore *sem, long timeout)
  */
 int ldsem_down_read_trylock(struct ld_semaphore *sem)
 {
-	long count = sem->count;
+	long count = atomic_long_read(&sem->count);
 
 	while (count >= 0) {
-		if (ldsem_cmpxchg(&count, count + LDSEM_READ_BIAS, sem)) {
-			lockdep_acquire_read(sem, 0, 1, _RET_IP_);
-			lock_stat(sem, acquired);
+		if (atomic_long_try_cmpxchg(&sem->count, &count, count + LDSEM_READ_BIAS)) {
+			rwsem_acquire_read(&sem->dep_map, 0, 1, _RET_IP_);
+			lock_acquired(&sem->dep_map, _RET_IP_);
 			return 1;
 		}
 	}
@@ -390,32 +367,15 @@ int __sched ldsem_down_write(struct ld_semaphore *sem, long timeout)
 }
 
 /*
- * trylock for writing -- returns 1 if successful, 0 if contention
- */
-int ldsem_down_write_trylock(struct ld_semaphore *sem)
-{
-	long count = sem->count;
-
-	while ((count & LDSEM_ACTIVE_MASK) == 0) {
-		if (ldsem_cmpxchg(&count, count + LDSEM_WRITE_BIAS, sem)) {
-			lockdep_acquire(sem, 0, 1, _RET_IP_);
-			lock_stat(sem, acquired);
-			return 1;
-		}
-	}
-	return 0;
-}
-
-/*
  * release a read lock
  */
 void ldsem_up_read(struct ld_semaphore *sem)
 {
 	long count;
 
-	lockdep_release(sem, 1, _RET_IP_);
+	rwsem_release(&sem->dep_map, _RET_IP_);
 
-	count = ldsem_atomic_update(-LDSEM_READ_BIAS, sem);
+	count = atomic_long_add_return(-LDSEM_READ_BIAS, &sem->count);
 	if (count < 0 && (count & LDSEM_ACTIVE_MASK) == 0)
 		ldsem_wake(sem);
 }
@@ -427,9 +387,9 @@ void ldsem_up_write(struct ld_semaphore *sem)
 {
 	long count;
 
-	lockdep_release(sem, 1, _RET_IP_);
+	rwsem_release(&sem->dep_map, _RET_IP_);
 
-	count = ldsem_atomic_update(-LDSEM_WRITE_BIAS, sem);
+	count = atomic_long_add_return(-LDSEM_WRITE_BIAS, &sem->count);
 	if (count < 0)
 		ldsem_wake(sem);
 }