2  * Copyright (c) 2010-2016 Wind River Systems, Inc.
4  * SPDX-License-Identifier: Apache-2.0
32 /* We use a system-wide lock to synchronize semaphores, which has
33  * unfortunate performance impact vs. using a per-object lock
34  * (semaphores are *very* widely used).  But per-object locks require
35  * significant extra RAM.  A properly spin-aware semaphore
39 static struct k_spinlock lock;  variable
52 		SYS_PORT_TRACING_OBJ_FUNC(k_sem, init, sem, -EINVAL);  in z_impl_k_sem_init()
54 		return -EINVAL;  in z_impl_k_sem_init()
57 	sem->count = initial_count;  in z_impl_k_sem_init()
58 	sem->limit = limit;  in z_impl_k_sem_init()
62 	z_waitq_init(&sem->wait_q);  in z_impl_k_sem_init()
64 	sys_dlist_init(&sem->poll_events);  in z_impl_k_sem_init()
88 	z_handle_obj_poll_events(&sem->poll_events, K_POLL_STATE_SEM_AVAILABLE);  in handle_poll_events()
98 	k_spinlock_key_t key = k_spin_lock(&lock);  in z_impl_k_sem_give()
104 	thread = z_unpend_first_thread(&sem->wait_q);  in z_impl_k_sem_give()
110 		sem->count += (sem->count != sem->limit) ? 1U : 0U;  in z_impl_k_sem_give()
115 		z_reschedule(&lock, key);  in z_impl_k_sem_give()
117 		k_spin_unlock(&lock, key);  in z_impl_k_sem_give()
139 	k_spinlock_key_t key = k_spin_lock(&lock);  in z_impl_k_sem_take()
143 	if (likely(sem->count > 0U)) {  in z_impl_k_sem_take()
144 		sem->count--;  in z_impl_k_sem_take()
145 		k_spin_unlock(&lock, key);  in z_impl_k_sem_take()
151 		k_spin_unlock(&lock, key);  in z_impl_k_sem_take()
152 		ret = -EBUSY;  in z_impl_k_sem_take()
158 	ret = z_pend_curr(&lock, key, &sem->wait_q, timeout);  in z_impl_k_sem_take()
169 	k_spinlock_key_t key = k_spin_lock(&lock);  in z_impl_k_sem_reset()
172 		thread = z_unpend_first_thread(&sem->wait_q);  in z_impl_k_sem_reset()
176 		arch_thread_return_value_set(thread, -EAGAIN);  in z_impl_k_sem_reset()
179 	sem->count = 0;  in z_impl_k_sem_reset()
185 	z_reschedule(&lock, key);  in z_impl_k_sem_reset()