559 lines
18 KiB
C
559 lines
18 KiB
C
/*
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* Copyright (c) 2006-2021, RT-Thread Development Team
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*
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* SPDX-License-Identifier: Apache-2.0
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*
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* Change Logs:
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* Date Author Notes
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* 2010-10-26 Bernard the first version
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*/
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#include <rtthread.h>
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#include <string.h>
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#include <fcntl.h>
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#include <sys/errno.h>
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#include "semaphore.h"
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static sem_t *posix_sem_list = RT_NULL;
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static struct rt_semaphore posix_sem_lock;
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/* initialize posix semaphore */
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static int posix_sem_system_init(void)
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{
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rt_sem_init(&posix_sem_lock, "psem", 1, RT_IPC_FLAG_FIFO);
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return 0;
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}
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INIT_COMPONENT_EXPORT(posix_sem_system_init);
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/**
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* @brief Inserts a semaphore into the linked list of semaphores.
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* @param psem Pointer to the semaphore structure to be inserted.
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*
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* @note This function inserts the specified semaphore into a linked list of semaphores.
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* The newly inserted semaphore becomes the head of the list.
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* It updates the 'next' pointer of the semaphore structure to link it to the
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* current head of the list and then sets the head of the list to point to the
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* newly inserted semaphore.
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*/
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rt_inline void posix_sem_insert(sem_t *psem)
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{
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psem->next = posix_sem_list;
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posix_sem_list = psem;
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}
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/**
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* @brief Deletes a semaphore from the linked list of semaphores.
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* @param psem Pointer to the semaphore structure to be deleted.
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*
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* @note This function deletes the specified semaphore from a linked list of semaphores.
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* If the semaphore to be deleted is the head of the list, it updates the head of the list
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* to point to the next semaphore. Otherwise, it traverses the list to find the semaphore
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* to be deleted and updates the 'next' pointer of the preceding semaphore to skip over
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* the semaphore to be deleted.
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* After deleting the semaphore, it also deletes the underlying RT-Thread semaphore if it exists
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* and frees the memory associated with the semaphore structure if it's not unnamed.
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*/
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static void posix_sem_delete(sem_t *psem)
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{
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sem_t *iter;
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if (posix_sem_list == psem)
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{
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posix_sem_list = psem->next;
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rt_sem_delete(psem->sem);
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if(psem->unamed == 0)
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rt_free(psem);
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return;
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}
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for (iter = posix_sem_list; iter->next != RT_NULL; iter = iter->next)
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{
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if (iter->next == psem)
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{
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/* delete this mq */
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if (psem->next != RT_NULL)
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iter->next = psem->next;
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else
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iter->next = RT_NULL;
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/* delete RT-Thread mqueue */
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rt_sem_delete(psem->sem);
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if(psem->unamed == 0)
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rt_free(psem);
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return ;
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}
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}
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}
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/**
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* @brief Finds a semaphore by name in the linked list of semaphores.
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* @param name Pointer to the name of the semaphore to be found.
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* @return Pointer to the semaphore structure if found; otherwise, RT_NULL.
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*
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* @note This function searches for a semaphore with the specified name in the linked list of semaphores.
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* It iterates through the list and compares the name of each semaphore with the given name.
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* If a semaphore with a matching name is found, a pointer to its structure is returned.
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* Otherwise, RT_NULL is returned to indicate that no semaphore with the given name was found.
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*/
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static sem_t *posix_sem_find(const char* name)
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{
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sem_t *iter;
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rt_object_t object;
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for (iter = posix_sem_list; iter != RT_NULL; iter = iter->next)
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{
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object = (rt_object_t)iter->sem;
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if (strncmp(object->name, name, RT_NAME_MAX) == 0)
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{
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return iter;
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}
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}
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return RT_NULL;
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}
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/**
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* @brief Closes a POSIX semaphore.
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* @param sem Pointer to the semaphore to be closed.
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* @return Upon successful completion, returns 0; otherwise, returns -1 and sets errno to indicate the error.
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*
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* @note This function decreases the reference count of the specified semaphore.
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* If the reference count reaches zero, the semaphore is removed from the list
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* of POSIX semaphores if it was unlinked. The memory associated with the semaphore
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* is not immediately freed; instead, it will be freed when the last reference to
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* the semaphore is released.
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*/
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int sem_close(sem_t *sem)
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{
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if (sem == RT_NULL)
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{
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rt_set_errno(EINVAL);
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return -1;
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}
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/* lock posix semaphore list */
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rt_sem_take(&posix_sem_lock, RT_WAITING_FOREVER);
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sem->refcount --;
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if (sem->refcount == 0)
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{
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/* delete from posix semaphore list */
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if (sem->unlinked)
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posix_sem_delete(sem);
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sem = RT_NULL;
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}
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rt_sem_release(&posix_sem_lock);
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return 0;
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}
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RTM_EXPORT(sem_close);
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/**
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* @brief Destroys a POSIX semaphore.
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* @param sem Pointer to the semaphore to be destroyed.
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* @return Upon successful completion, returns 0; otherwise, returns -1 and sets errno to indicate the error.
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*
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* @note This function destroys an unnamed POSIX semaphore.
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* It first checks if the semaphore pointer is valid and if the semaphore is unnamed.
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* If the semaphore is still in use (i.e., there are threads waiting on it),
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* the function returns with an error code (EBUSY) without destroying the semaphore.
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* Otherwise, it removes the semaphore from the list of POSIX semaphores and frees
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* the memory associated with the semaphore structure.
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*/
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int sem_destroy(sem_t *sem)
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{
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if ((!sem) || !(sem->unamed))
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{
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rt_set_errno(EINVAL);
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return -1;
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}
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/* lock posix semaphore list */
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rt_sem_take(&posix_sem_lock, RT_WAITING_FOREVER);
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if(rt_list_len(&sem->sem->parent.suspend_thread) != 0)
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{
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rt_sem_release(&posix_sem_lock);
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rt_set_errno(EBUSY);
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return -1;
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}
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/* destroy an unamed posix semaphore */
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posix_sem_delete(sem);
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rt_sem_release(&posix_sem_lock);
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return 0;
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}
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RTM_EXPORT(sem_destroy);
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/**
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* @brief Unlinks a named POSIX semaphore.
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* @param name Pointer to the name of the semaphore to be unlinked.
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* @return Upon successful completion, returns 0; otherwise, returns -1 and sets errno to indicate the error.
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*
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* @note This function unlinks a named POSIX semaphore identified by the given name.
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* It first searches for the semaphore with the specified name in the list of
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* POSIX semaphores. If the semaphore is found, it marks the semaphore as unlinked.
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* If the reference count of the semaphore is zero, indicating that no threads are
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* currently using the semaphore, it removes the semaphore from the list and frees
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* the associated memory. Otherwise, the semaphore is not immediately removed; it
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* will be removed when its reference count reaches zero.
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*/
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int sem_unlink(const char *name)
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{
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sem_t *psem;
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/* lock posix semaphore list */
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rt_sem_take(&posix_sem_lock, RT_WAITING_FOREVER);
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psem = posix_sem_find(name);
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if (psem != RT_NULL)
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{
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psem->unlinked = 1;
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if (psem->refcount == 0)
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{
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/* remove this semaphore */
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posix_sem_delete(psem);
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}
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rt_sem_release(&posix_sem_lock);
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return 0;
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}
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rt_sem_release(&posix_sem_lock);
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/* no this entry */
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rt_set_errno(ENOENT);
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return -1;
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}
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RTM_EXPORT(sem_unlink);
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/**
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* @brief Retrieves the value of a POSIX semaphore.
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* @param sem Pointer to the semaphore.
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* @param sval Pointer to an integer where the semaphore value will be stored.
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* @return Upon successful completion, returns 0; otherwise, returns -1 and sets errno to indicate the error.
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*
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* @note This function retrieves the current value of the specified POSIX semaphore.
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* It copies the semaphore value into the memory location pointed to by sval.
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* If either sem or sval is a null pointer, the function sets errno to EINVAL
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* to indicate an invalid argument and returns -1.
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*/
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int sem_getvalue(sem_t *sem, int *sval)
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{
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if (!sem || !sval)
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{
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rt_set_errno(EINVAL);
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return -1;
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}
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*sval = sem->sem->value;
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return 0;
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}
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RTM_EXPORT(sem_getvalue);
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/**
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* @brief Initializes a POSIX semaphore.
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* @param sem Pointer to the semaphore structure to be initialized.
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* @param pshared Flag indicating whether the semaphore is to be shared between processes.
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* @param value Initial value of the semaphore.
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* @return Upon successful completion, returns 0; otherwise, returns -1 and sets errno to indicate the error.
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*
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* @note This function initializes a POSIX semaphore with the specified initial value.
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* If sem is a null pointer, the function sets errno to EINVAL to indicate an invalid argument and returns -1.
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* The pshared parameter is not used in this implementation, as all semaphores are created as local (unshared).
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* The value parameter specifies the initial value of the semaphore.
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* The semaphore is given a unique name using a static counter, and it is created using the RT-Thread semaphore
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* creation function rt_sem_create(). If memory allocation fails during semaphore creation, errno is set to ENOMEM.
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* After successful initialization, the semaphore structure is inserted into the linked list of POSIX semaphores.
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*/
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int sem_init(sem_t *sem, int pshared, unsigned int value)
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{
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char name[RT_NAME_MAX];
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static rt_uint16_t psem_number = 0;
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if (sem == RT_NULL)
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{
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rt_set_errno(EINVAL);
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return -1;
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}
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rt_snprintf(name, sizeof(name), "psem%02d", psem_number++);
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sem->sem = rt_sem_create(name, value, RT_IPC_FLAG_FIFO);
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if (sem->sem == RT_NULL)
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{
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rt_set_errno(ENOMEM);
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return -1;
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}
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/* initialize posix semaphore */
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sem->refcount = 1;
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sem->unlinked = 0;
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sem->unamed = 1;
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/* lock posix semaphore list */
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rt_sem_take(&posix_sem_lock, RT_WAITING_FOREVER);
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posix_sem_insert(sem);
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rt_sem_release(&posix_sem_lock);
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return 0;
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}
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RTM_EXPORT(sem_init);
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/**
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* @brief Opens or creates a POSIX semaphore.
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* @param name Pointer to the name of the semaphore.
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* @param oflag Bitwise OR of flags indicating the operation mode.
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* @param ... Additional arguments (optional).
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* @return Upon successful completion, returns a pointer to the semaphore;
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* otherwise, returns RT_NULL and sets errno to indicate the error.
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*
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* @note This function opens or creates a POSIX semaphore specified by the name argument.
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* If the oflag argument includes O_CREAT, the semaphore is created if it does not already exist.
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* Additional arguments may include the mode (not used in this implementation) and the initial value of the semaphore.
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* If the oflag argument includes O_EXCL along with O_CREAT, the function fails if the semaphore already exists.
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* If memory allocation fails during semaphore creation, errno is set to ENFILE.
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* After successful creation or opening, the semaphore's reference count is incremented, and it is inserted into
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* the linked list of POSIX semaphores. If the semaphore already exists and is successfully opened, its reference
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* count is incremented. If the semaphore cannot be opened or created for any reason, errno is set to indicate the error,
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* and the function returns RT_NULL.
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*/
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sem_t *sem_open(const char *name, int oflag, ...)
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{
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sem_t* sem;
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va_list arg;
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mode_t mode;
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unsigned int value;
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sem = RT_NULL;
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/* lock posix semaphore list */
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rt_sem_take(&posix_sem_lock, RT_WAITING_FOREVER);
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if (oflag & O_CREAT)
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{
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va_start(arg, oflag);
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mode = (mode_t) va_arg( arg, unsigned int); mode = mode;
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value = va_arg( arg, unsigned int);
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va_end(arg);
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if (oflag & O_EXCL)
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{
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if (posix_sem_find(name) != RT_NULL)
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{
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rt_set_errno(EEXIST);
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goto __return;
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}
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}
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sem = (sem_t*) rt_malloc (sizeof(struct posix_sem));
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if (sem == RT_NULL)
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{
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rt_set_errno(ENFILE);
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goto __return;
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}
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/* create RT-Thread semaphore */
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sem->sem = rt_sem_create(name, value, RT_IPC_FLAG_FIFO);
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if (sem->sem == RT_NULL) /* create failed */
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{
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rt_set_errno(ENFILE);
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goto __return;
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}
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/* initialize reference count */
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sem->refcount = 1;
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sem->unlinked = 0;
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sem->unamed = 0;
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/* insert semaphore to posix semaphore list */
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posix_sem_insert(sem);
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}
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else
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{
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/* find semaphore */
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sem = posix_sem_find(name);
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if (sem != RT_NULL)
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{
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sem->refcount ++; /* increase reference count */
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}
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else
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{
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rt_set_errno(ENOENT);
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goto __return;
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}
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}
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rt_sem_release(&posix_sem_lock);
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return sem;
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__return:
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/* release lock */
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rt_sem_release(&posix_sem_lock);
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/* release allocated memory */
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if (sem != RT_NULL)
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{
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/* delete RT-Thread semaphore */
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if (sem->sem != RT_NULL)
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rt_sem_delete(sem->sem);
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rt_free(sem);
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}
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return RT_NULL;
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}
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RTM_EXPORT(sem_open);
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/**
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* @brief Posts (increments) a POSIX semaphore.
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* @param sem Pointer to the semaphore.
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* @return Upon successful completion, returns 0; otherwise, returns -1 and sets errno to indicate the error.
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*
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* @note This function increments the value of the specified POSIX semaphore by one.
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* If sem is a null pointer, errno is set to EINVAL to indicate an invalid argument, and the function returns -1.
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* The semaphore is released using the RT-Thread semaphore release function rt_sem_release().
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* If the semaphore release operation succeeds, the function returns 0; otherwise, errno is set to EINVAL,
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* indicating an error, and the function returns -1.
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*/
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int sem_post(sem_t *sem)
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{
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rt_err_t result;
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if (!sem)
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{
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rt_set_errno(EINVAL);
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return -1;
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}
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result = rt_sem_release(sem->sem);
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if (result == RT_EOK)
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return 0;
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rt_set_errno(EINVAL);
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return -1;
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}
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RTM_EXPORT(sem_post);
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/**
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* @brief Waits for a POSIX semaphore with a timeout.
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* @param sem Pointer to the semaphore.
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* @param abs_timeout Pointer to the absolute timeout value.
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* @return Upon successful completion, returns 0; otherwise, returns -1 and sets errno to indicate the error.
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*
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* @note This function waits for the specified POSIX semaphore to become available within the specified timeout.
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* If either sem or abs_timeout is a null pointer, the function returns EINVAL, indicating an invalid argument.
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* The abs_timeout parameter specifies an absolute timeout value based on the CLOCK_REALTIME clock.
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* The timeout is converted to RT-Thread ticks using the rt_timespec_to_tick() function.
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* The semaphore is waited upon using the RT-Thread semaphore take function rt_sem_take().
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* If the semaphore is successfully acquired within the specified timeout, the function returns 0.
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* If the timeout expires before the semaphore becomes available, errno is set to ETIMEDOUT,
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* and the function returns -1. If the semaphore wait operation is interrupted by a signal,
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* errno is set to EINTR, and the function returns -1.
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*/
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int sem_timedwait(sem_t *sem, const struct timespec *abs_timeout)
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{
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rt_err_t result;
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rt_int32_t tick;
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if (!sem || !abs_timeout)
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return EINVAL;
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/* calculate os tick */
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tick = rt_timespec_to_tick(abs_timeout);
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result = rt_sem_take(sem->sem, tick);
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if (result == -RT_ETIMEOUT)
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{
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rt_set_errno(ETIMEDOUT);
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return -1;
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}
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if (result == RT_EOK)
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return 0;
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rt_set_errno(EINTR);
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return -1;
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}
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RTM_EXPORT(sem_timedwait);
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/**
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* @brief Attempts to wait for a POSIX semaphore without blocking.
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* @param sem Pointer to the semaphore.
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* @return Upon successful completion, returns 0 if the semaphore was acquired;
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* otherwise, returns -1 and sets errno to indicate the error.
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*
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* @note This function attempts to acquire the specified POSIX semaphore without blocking.
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* If sem is a null pointer, errno is set to EINVAL to indicate an invalid argument, and the function returns -1.
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* The semaphore is waited upon using the RT-Thread semaphore take function rt_sem_take() with a timeout of 0,
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* meaning that the function does not block if the semaphore is not available.
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* If the semaphore is successfully acquired, the function returns 0. If the semaphore is not available,
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* errno is set to EAGAIN to indicate that the operation would result in blocking, and the function returns -1.
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* If the semaphore wait operation is interrupted by a signal, errno is set to EINTR, and the function returns -1.
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*/
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int sem_trywait(sem_t *sem)
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{
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rt_err_t result;
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if (!sem)
|
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{
|
|
rt_set_errno(EINVAL);
|
|
|
|
return -1;
|
|
}
|
|
|
|
result = rt_sem_take(sem->sem, 0);
|
|
if (result == -RT_ETIMEOUT)
|
|
{
|
|
rt_set_errno(EAGAIN);
|
|
|
|
return -1;
|
|
}
|
|
if (result == RT_EOK)
|
|
return 0;
|
|
|
|
rt_set_errno(EINTR);
|
|
|
|
return -1;
|
|
}
|
|
RTM_EXPORT(sem_trywait);
|
|
|
|
/**
|
|
* @brief Waits indefinitely for a POSIX semaphore to become available.
|
|
* @param sem Pointer to the semaphore.
|
|
* @return Upon successful completion, returns 0; otherwise, returns -1 and sets errno to indicate the error.
|
|
*
|
|
* @note This function waits indefinitely for the specified POSIX semaphore to become available.
|
|
* If sem is a null pointer, errno is set to EINVAL to indicate an invalid argument, and the function returns -1.
|
|
* The semaphore is waited upon using the RT-Thread semaphore take function rt_sem_take() with a timeout
|
|
* value of RT_WAITING_FOREVER, indicating an infinite wait time.
|
|
* If the semaphore is successfully acquired, the function returns 0. If the semaphore wait operation is interrupted
|
|
* by a signal, errno is set to EINTR, and the function returns -1.
|
|
*/
|
|
int sem_wait(sem_t *sem)
|
|
{
|
|
rt_err_t result;
|
|
|
|
if (!sem)
|
|
{
|
|
rt_set_errno(EINVAL);
|
|
|
|
return -1;
|
|
}
|
|
|
|
result = rt_sem_take(sem->sem, RT_WAITING_FOREVER);
|
|
if (result == RT_EOK)
|
|
return 0;
|
|
|
|
rt_set_errno(EINTR);
|
|
|
|
return -1;
|
|
}
|
|
RTM_EXPORT(sem_wait);
|
|
|