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