drivers/tty/tty_ldsem.c

12  *   1) Upper half of semaphore count is a wait count (differs from rwsem
67 	atomic_long_set(&sem->count, LDSEM_UNLOCKED);
78 	long adjust, count;
82 	 * Note the 'active part' of the count is incremented by
86 	count = atomic_long_add_return(adjust, &sem->count);
88 		if (count > 0)
90 		if (atomic_long_try_cmpxchg(&sem->count, &count, count - adjust))
107 	 * Only wake this writer if the active part of the count can be
110 	long count = atomic_long_add_return(LDSEM_ACTIVE_BIAS, &sem->count);
112 		if ((count & LDSEM_ACTIVE_MASK) == LDSEM_ACTIVE_BIAS)
114 		if (atomic_long_try_cmpxchg(&sem->count, &count, count - LDSEM_ACTIVE_BIAS))
130  *   - the 'active part' of count (&0x0000ffff) reached 0 (but may have changed)
131  *   - the 'waiting part' of count (&0xffff0000) is -ve (and will still be so)
156 down_read_failed(struct ld_semaphore *sem, long count, long timeout)
165 	 * Try to reverse the lock attempt but if the count has changed
170 		if (atomic_long_try_cmpxchg(&sem->count, &count, count + adjust)) {
171 			count += adjust;
174 		if (count > 0) {
187 	if ((count & LDSEM_ACTIVE_MASK) == 0)
213 			atomic_long_add_return(-LDSEM_WAIT_BIAS, &sem->count);
230 down_write_failed(struct ld_semaphore *sem, long count, long timeout)
240 	 * Try to reverse the lock attempt but if the count has changed
245 		if (atomic_long_try_cmpxchg(&sem->count, &count, count + adjust))
247 		if ((count & LDSEM_ACTIVE_MASK) == LDSEM_ACTIVE_BIAS) {
271 		atomic_long_add_return(-LDSEM_WAIT_BIAS, &sem->count);
298 	long count;
302 	count = atomic_long_add_return(LDSEM_READ_BIAS, &sem->count);
303 	if (count <= 0) {
305 		if (!down_read_failed(sem, count, timeout)) {
317 	long count;
321 	count = atomic_long_add_return(LDSEM_WRITE_BIAS, &sem->count);
322 	if ((count & LDSEM_ACTIVE_MASK) != LDSEM_ACTIVE_BIAS) {
324 		if (!down_write_failed(sem, count, timeout)) {
348 	long count = atomic_long_read(&sem->count);
350 	while (count >= 0) {
351 		if (atomic_long_try_cmpxchg(&sem->count, &count, count + LDSEM_READ_BIAS)) {
374 	long count;
378 	count = atomic_long_add_return(-LDSEM_READ_BIAS, &sem->count);
379 	if (count < 0 && (count & LDSEM_ACTIVE_MASK) == 0)
388 	long count;
392 	count = atomic_long_add_return(-LDSEM_WRITE_BIAS, &sem->count);
393 	if (count < 0)