Add some comments in components/libc/posix/ipc/semaphore.c (#8848)
This commit is contained in:
Troy
GitHub
parent
2c8c4ccc47
commit
98a234d430
|
|
@ -25,12 +25,34 @@ static int posix_sem_system_init(void)
|
|||
}
|
||||
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;
|
||||
|
|
@ -66,6 +88,16 @@ static void posix_sem_delete(sem_t *psem)
|
|||
}
|
||||
}
|
||||
|
||||
/**
|
||||
* @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;
|
||||
|
|
@ -84,6 +116,17 @@ static sem_t *posix_sem_find(const char* name)
|
|||
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)
|
||||
|
|
@ -109,6 +152,18 @@ int sem_close(sem_t *sem)
|
|||
}
|
||||
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))
|
||||
|
|
@ -136,6 +191,19 @@ int sem_destroy(sem_t *sem)
|
|||
}
|
||||
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;
|
||||
|
|
@ -164,6 +232,17 @@ int sem_unlink(const char *name)
|
|||
}
|
||||
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)
|
||||
|
|
@ -178,6 +257,21 @@ int sem_getvalue(sem_t *sem, int *sval)
|
|||
}
|
||||
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];
|
||||
|
|
@ -212,6 +306,24 @@ int sem_init(sem_t *sem, int pshared, unsigned int value)
|
|||
}
|
||||
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;
|
||||
|
|
@ -295,6 +407,17 @@ __return:
|
|||
}
|
||||
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;
|
||||
|
|
@ -316,6 +439,22 @@ int sem_post(sem_t *sem)
|
|||
}
|
||||
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;
|
||||
|
|
@ -343,6 +482,20 @@ int sem_timedwait(sem_t *sem, const struct timespec *abs_timeout)
|
|||
}
|
||||
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;
|
||||
|
|
@ -370,6 +523,18 @@ int sem_trywait(sem_t *sem)
|
|||
}
|
||||
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;
|
||||
|
|
|
|||
Loading…
Reference in New Issue