blob: ee2d3079f7c8b05f20ac941927a2c7d62d9035a5 [file] [log] [blame]
/*
* Copyright (c) 2010-2016 Wind River Systems, Inc.
*
* SPDX-License-Identifier: Apache-2.0
*/
/**
* @file
*
* @brief Kernel semaphore object.
*
* The semaphores are of the 'counting' type, i.e. each 'give' operation will
* increment the internal count by 1, if no thread is pending on it. The 'init'
* call initializes the count to 'initial_count'. Following multiple 'give'
* operations, the same number of 'take' operations can be performed without
* the calling thread having to pend on the semaphore, or the calling task
* having to poll.
*/
#include <kernel.h>
#include <kernel_structs.h>
#include <toolchain.h>
#include <wait_q.h>
#include <sys/dlist.h>
#include <ksched.h>
#include <init.h>
#include <syscall_handler.h>
#include <tracing/tracing.h>
#include <sys/check.h>
/* We use a system-wide lock to synchronize semaphores, which has
* unfortunate performance impact vs. using a per-object lock
* (semaphores are *very* widely used). But per-object locks require
* significant extra RAM. A properly spin-aware semaphore
* implementation would spin on atomic access to the count variable,
* and not a spinlock per se. Useful optimization for the future...
*/
static struct k_spinlock lock;
int z_impl_k_sem_init(struct k_sem *sem, unsigned int initial_count,
unsigned int limit)
{
/*
* Limit cannot be zero and count cannot be greater than limit
*/
CHECKIF(limit == 0U || limit > K_SEM_MAX_LIMIT || initial_count > limit) {
SYS_PORT_TRACING_OBJ_FUNC(k_sem, init, sem, -EINVAL);
return -EINVAL;
}
sem->count = initial_count;
sem->limit = limit;
SYS_PORT_TRACING_OBJ_FUNC(k_sem, init, sem, 0);
z_waitq_init(&sem->wait_q);
#if defined(CONFIG_POLL)
sys_dlist_init(&sem->poll_events);
#endif
z_object_init(sem);
return 0;
}
#ifdef CONFIG_USERSPACE
int z_vrfy_k_sem_init(struct k_sem *sem, unsigned int initial_count,
unsigned int limit)
{
Z_OOPS(Z_SYSCALL_OBJ_INIT(sem, K_OBJ_SEM));
return z_impl_k_sem_init(sem, initial_count, limit);
}
#include <syscalls/k_sem_init_mrsh.c>
#endif
static inline void handle_poll_events(struct k_sem *sem)
{
#ifdef CONFIG_POLL
z_handle_obj_poll_events(&sem->poll_events, K_POLL_STATE_SEM_AVAILABLE);
#else
ARG_UNUSED(sem);
#endif
}
void z_impl_k_sem_give(struct k_sem *sem)
{
k_spinlock_key_t key = k_spin_lock(&lock);
struct k_thread *thread;
SYS_PORT_TRACING_OBJ_FUNC_ENTER(k_sem, give, sem);
thread = z_unpend_first_thread(&sem->wait_q);
if (thread != NULL) {
arch_thread_return_value_set(thread, 0);
z_ready_thread(thread);
} else {
sem->count += (sem->count != sem->limit) ? 1U : 0U;
handle_poll_events(sem);
}
z_reschedule(&lock, key);
SYS_PORT_TRACING_OBJ_FUNC_EXIT(k_sem, give, sem);
}
#ifdef CONFIG_USERSPACE
static inline void z_vrfy_k_sem_give(struct k_sem *sem)
{
Z_OOPS(Z_SYSCALL_OBJ(sem, K_OBJ_SEM));
z_impl_k_sem_give(sem);
}
#include <syscalls/k_sem_give_mrsh.c>
#endif
int z_impl_k_sem_take(struct k_sem *sem, k_timeout_t timeout)
{
int ret = 0;
__ASSERT(((arch_is_in_isr() == false) ||
K_TIMEOUT_EQ(timeout, K_NO_WAIT)), "");
k_spinlock_key_t key = k_spin_lock(&lock);
SYS_PORT_TRACING_OBJ_FUNC_ENTER(k_sem, take, sem, timeout);
if (likely(sem->count > 0U)) {
sem->count--;
k_spin_unlock(&lock, key);
ret = 0;
goto out;
}
if (K_TIMEOUT_EQ(timeout, K_NO_WAIT)) {
k_spin_unlock(&lock, key);
ret = -EBUSY;
goto out;
}
SYS_PORT_TRACING_OBJ_FUNC_BLOCKING(k_sem, take, sem, timeout);
ret = z_pend_curr(&lock, key, &sem->wait_q, timeout);
out:
SYS_PORT_TRACING_OBJ_FUNC_EXIT(k_sem, take, sem, timeout, ret);
return ret;
}
void z_impl_k_sem_reset(struct k_sem *sem)
{
struct k_thread *thread;
k_spinlock_key_t key = k_spin_lock(&lock);
while (true) {
thread = z_unpend_first_thread(&sem->wait_q);
if (thread == NULL) {
break;
}
arch_thread_return_value_set(thread, -EAGAIN);
z_ready_thread(thread);
}
sem->count = 0;
SYS_PORT_TRACING_OBJ_FUNC(k_sem, reset, sem);
handle_poll_events(sem);
z_reschedule(&lock, key);
}
#ifdef CONFIG_USERSPACE
static inline int z_vrfy_k_sem_take(struct k_sem *sem, k_timeout_t timeout)
{
Z_OOPS(Z_SYSCALL_OBJ(sem, K_OBJ_SEM));
return z_impl_k_sem_take((struct k_sem *)sem, timeout);
}
#include <syscalls/k_sem_take_mrsh.c>
static inline void z_vrfy_k_sem_reset(struct k_sem *sem)
{
Z_OOPS(Z_SYSCALL_OBJ(sem, K_OBJ_SEM));
z_impl_k_sem_reset(sem);
}
#include <syscalls/k_sem_reset_mrsh.c>
static inline unsigned int z_vrfy_k_sem_count_get(struct k_sem *sem)
{
Z_OOPS(Z_SYSCALL_OBJ(sem, K_OBJ_SEM));
return z_impl_k_sem_count_get(sem);
}
#include <syscalls/k_sem_count_get_mrsh.c>
#endif