Description
Changes the current value of the semaphore count. This function is normally selected when a semaphore is used as a signaling mechanism. OSSemSet() can then be used to reset the count to any value. If the semaphore count is already 0, the count is only changed if there are no tasks waiting on the semaphore.
Files
os.h/os_sem.c
Prototype
Arguments
p_sem
is a pointer to the semaphore that is used as a signaling mechanism.
cnt
is the desired count that the semaphore should be set to.
p_err
is a pointer to a variable used to hold an error code:
OS_ERR_NONE
If the count was changed or, not changed, because one or more tasks was waiting on the semaphore.
OS_ERR_OBJ_PTR_NULL
If OS_CFG_ARG_CHK_EN is set to 1 in os_cfg.h: if p_sem is a NULL pointer.
OS_ERR_OBJ_TYPE
If OS_CFG_OBJ_TYPE_CHK_EN is set to 1 in os_cfg.h: if p_sem is not pointing to a semaphore.
OS_ERR_SET_ISR
If OS_CFG_CALLED_FROM_ISR_CHK_EN set to 1 in os_cfg.h: if this function was called from an ISR.
OS_ERR_TASK_WAITING
If tasks are waiting on the semaphore.
Returned Value
None
Required Configuration
OS_CFG_SEM_EN and OS_CFG_SEM_SET_EN must be enabled in os_cfg.h. Refer to uC-OS-III Configuration Manual
Callers
Application.
Notes/Warnings
- Do not use this function if the semaphore is used to protect a shared resource.